The primary purpose of a front mount intercooler is to reduce post turbo air temperature prior to entering the combustion chamber via the throttle body.

HP gain is around 15HP. This figure can vary as results can be further enhanced with post installation tuning. This is one modification that is extremely difficult to put a traditional HP figure on as results truly vary from car to car based on tuning and turbo output in terms of CFM.
FMIC dyno test
FMIC dyno test

Which manufacturer is best? This topic is highly debated. There have been no reported consistent "bad" FMICs on the market. Obviously, there may have been bad FMICs sold, but not enough to report as "bad" overall.

Which FMIC construction method is best? FMICs have two main construction methods:
1. tube and fin
2. bar and plate
There is much debate as to which construction method is best. There are many pros and cons with each design type, but no real hard data. Bar and plate designs are consistently reported as more damage resistant which gives them the edge with regard to appearance longevity. In the end, you are best advised to chose a FMIC based on other qualities rather than concentrate on construction design.

Which FMIC has the best gains? There is no irrefutable evidence that any FMIC has better gains than another. The consensus, if there is one, is they are all within 5HP or less, gain wise, of each other.

I have a 2006/2007 model, any differences? Yes. There were slight engine bay changes in these years, so there are issues with fitment on these years depending on the manufacturer. Check with your vendor prior to purchasing to sort these issues out.

I have a 2008/2009 model, any differences? Yes. Your engine bay has an entirely new layout vs. the 2002-2007 models. Most of the models listed below are for the older models, so you will have to refer to the manufacturer/retailer for fitment, or use this link as a general guide.

Will a FMIC work with my OEM or JDM foglights? It depends on the year/model and your foglights. Refer to the manufacturer/retailer for fitment issues with foglights.

What is the best size FMIC to buy for my turbo? This topic is highly debated. The two general trains of thought are:
a. Bigger is better
b. A FMIC should be purchased based on need
For those willing to do their homework on what particular size would show the most benefit with the least amount of drawbacks, this article outlines the steps necessary to calculate the "best" size.

Are there any downsides to FMICs? There have not been significant amounts of problems with FMICs. Care should be taken by the end users to ensure through the Vendor that any special fitment requirements are discussed and understood prior to purchasing. Even "bolt on" intercoolers maybe have slight issues that you need to be aware of prior to purchasing. STi owners need to specifically ask about fitment as the majority of FMICs on the market were designed for the WRX. Other things to talk over with your Vendor prior to purchasing:
1. Will this FMIC come with a replacement bumper beam or will it require modifying the stock unit?
2. Will this FMIC require any modification to the bumper skin?
3. BOV use. Can this FMIC use the stock unit or accommodate an aftermarket BOV made by XXX? Some FMICs have issues with certain BOVs so it is better to determine what manufacturer/type of BOV you need prior to purchasing your FMIC to ensure a proper fit.
4. Intake use. Can this FMIC accommodate an aftermarket intake by XXX? Some FMICs have issues with certain intakes so it is better to determine what manufacturer/type of intake you need prior to purchasing your FMIC to ensure a proper fit.
5. Can I still use the stock foglights?
6. Does this FMIC have any issues with the placement of any underhood components such as the battery, coolant reservoir, etc.?
7. Can I use this FMIC on a wagon?
8. I have a 2006....will this fit?

What are the hidden costs with FMICs? When switching to a larger FMIC, you will face the additional expense of an aftermarket intake. You may also have to use a specific type of BOV.

What about the additional lag of a FMIC? This topic is highly debated. The two general trains of thought are:
1. FMICs increase turbo lag.
2. FMICs decrease throttle response.
Though there is much debate as to which one is actually correct, many believe that lack of heat soak issues of a TMIC are enough benefit to overcome the associated lower RPM issues of the FMIC.

Once I have a larger FMIC, what steps are helpful to increase its efficiency?
1. Waterspray. There are aftermarket waterspray options that provide increased cooling efficiency.
2. NO2 and CO2 Sprayers. There are aftermarket kits that spray CO2 or NO2 to that provide increased cooling efficiency.
3. Wrapping the return piping of the FMIC. Heat wrapping the return pipe is an excellent way of keeping the cooled air cool. Some FMICs come coated for appearance, but lack the heat reflecting ability of true heat blankets. Though not exactly eye appealing, the heat wrap serves it's function well for those wanting the most out of their FMIC.

Though sighting TMICs as examples, these two articles highlight how proper airflow and waterspray can increase your efficiency:
Article
Article

What insurance items should be considered with a FMIC? There are two things to consider with regard to insurance for your FMIC:
1. FMICs come with a replacement bumper beam or require modification of the stock unit. Either option could increase occupant or equipment injury in the event of a frontal accident. Though not proven, your insurance company could raise this issue if they find out.
2. A FMIC is a very expensive modification. Some insurance companies insure mods, some don't. This is one modification where it's worth a phone call to your agent to ensure its replacement value is covered in an accident.

Where do I buy a FMIC? Every Subaru/Import performance store sells FMICs. For purchasing, support your local economy or the NASIOC Vendors.

How hard is it to install a FMIC? Allow around five to eight hours for install time. Professional installation, depending on your area, is around $400. Shadetree mechanics will install for around $100. Friends and install parties via your local Subaru club run the cost of beer and food.

How do I install a FMIC? Refer to the FMIC manufacturer's instructions. For FMICs without instructions, below is a link to some of the better known installation instructions:
APS FMIC installation guide (725)
APS FMIC installation guide (650)
APS FMIC installation guide (500)
APS FMIC installation guide (DR 525)
Perrin Instructions

Should I reset my ECU after this mod? It is never a bad idea to perform an ECU reset after a mod. The traditional route is to disconnect the negative battery terminal press the brake pedal for a few seconds to bleed the system of charge, and reattach. Some use the more advanced Vishnu Reset.

Do I need tuning with a FMIC? In almost every circumstance, yes. This is mainly due to the addition of an aftermarket intake, which will generally affect your air/fuel ratios. The smart choice is to tune for the intake and at the same time tuning will allow greater utilization of the effects of the increased cooling. The one exception is the Cosworth 08/09 FMIC which is designed to work with the OEM intake, so no tuning is required if using that unit with the OEM intake.

What are some other good sources of FMIC information?
a. Bell Intercoolers' FAQ
b. ARE Cooling's tech article

Which is better a FMIC or a TMIC? There is no definate answer for this. Choose your upgraded intercooler based on the pros and cons of each and your personal goals. Perfect testing of intercoolers is not possible and though not specifically catered towards intercoolers, this Car and Driver magazine article will help point out the reasons why we will never know which is "better".

Comparative Data

Manufacturers of FMICs

APS
ARC
AVO
Blitz
CSS
Cosworth (08+ STI only)
GReddy
HKS
Hyperflow
Injen
OBX Racing
P&L Motorsports
Perrin
Process West
MRT
TurboXS
WBR
XO2 Racing

Pressure Drop

Pressure drop can change based on manufacturer's testing levels. Generally speaking, the higher the turbo PSI, the higher the pressure drop. Manufacturers often quote the lowest testing levels and often times do not quote their test data. This means you cannot compare intercooler A VS. intercooler B.

APS: 1.3 psi (500) 0.5 (650) 1.0 (725) (these figure vary with turbo PSI)
ARC: Unknown PSI
AVO: >1 PSI
Blitz: .05kg/cm2 at 1.2kg/cm2 of boost
CSS: 1 PSI at 18 PSI
Cosworth: Unknown PSI
GReddy: Unknown PSI
HKS: Unknown PSI
Hyperflow: Unknown PSI
Injen: .07 PSI
OBX: Unknown PSI
P&L Motorsports: Unknown PSI
Perrin: 1/4 PSI at 20 PSI
Process West: Unkown PSI
MRT: Unknown PSI
TurboXS: Unknown PSI
WBR: Unknown PSI
XO2 Racing: Unknown PSI

Core Construction

APS: tube and fin (500), bar and plate (650), bar and plate (750), bar and plate (525)
ARC: tube and fin
AVO: bar and plate
Blitz: tube and fin
CSS: bar and plate
Cosworth: bar and plate
GReddy: tube and fin
HKS: tube and fin (est.)
Hyperflow: bar and plate
Injen: bar and plate
OBX: tube and fin (est.)
P&L Motorsports: bar and plate
Perrin: bar and plate
Process West: bar and plate (est.)
MRT: bar and plate
TurboXS: bar and plate
WBR: bar and plate (est.)
XO2 Racing: bar and plate (est.)

Physical size

APS: 9.5" x 33.5" x 2.5" (500), 9.5" x 28" x 4.5" (650) 9.5" x 28 x 4.5" (725) 3 1/4" x 9 3/8" x 33 1/2" (525)
ARC: 9.5" x 22.5" x 3"
AVO: 8.8" x 23.5" x 3.5"
Blitz: 10.5" x 24" x 2.7"
CSS: 9" x 29" x 3.7"
Cosworth: 18" x 12.1" x 3" (08/09 model)
GReddy: 9.6" x 23.6" x 3" (based on metric conversion)
HKS: 9.6" x 23.6" x 2.5" (based on metric conversion)
Hyperflow: 9.4" x 26.3" x 3.5" (based on metric conversion) or 10” x 30” x 4.5” (Monster version)
Injen: 6.25" x 23.5" x 3"
OBX: 9" x 20" 2.5"
P&L Motorsports: 10" x 25" x 3.25"
Perrin: 9" x 28" x 3.6"
Process West: 9.25" x 25" x 3.5" (based on metric conversion)
MRT: 8" x 28" x 4"
TurboXS: 9.5" x 29.5 x 3.5" (02-07 model) 9.5" x 25.5" x 3.5" (08/09 model)
WBR: 9" x 30" x 3"
XO2 Racing: 9" x 24" x 3" or 12" x 24" x 3"

Do I need engine management/tuning with a FMIC? Yes. Since all FMICs use an intake of some kind, you will need tuning and engine management to ensure safety and performance from your new FMIC.