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2015-2020 WRX MT Upgrade info.

In Progress 2015+ WRX Build Guide

2015+ WRX FA20DIT Mod INFO.


Here is some information we have put together to help get you long-lasting enjoyment out of your FA20 powered WRX.

This list grows this is just a starting point. We hope to make it useful to all in the community in a fun guide to modding the fa20 while retaining reliability while having more power!


First up, Understand the FA20 is still a MAF-based car meaning anytime you do anything to change airflow across the maf the ECU will need to be programmed for this.



The new engine Subaru started to use in the 2015 + WRX. It's a direct-injected turbo motor that does require some special care.  We hope that this guide can serve as an aid to your performance route. Even if you're not using us for a tune we feel this is a solid path to follow.


Intakes:   We Prefer the  Cobb, ETS, AEM All of them must have a box or heat shield.( "Why is this important?" The maf sensor measures the airflow in the intake pipe. Which is mounted just behind the fans in your car.   Hot radiator 190+ Fan's drawing air into radiator.... Blowing it directly into your intake...  Bad idea, If you have one now without a box, simply check your intake temps on your cobb by pulling up "Intake temp Pre turbo" Not only is the temperature an issue but at idle the air from the radiator or ac fan will blow into maf and cause a disturbance in airflow causing poor idle and drifting fuel trims. )The stock ECU pulls out 3* of timing at 104* intake temp.  

If you are tuning a stock car, the gains of the intake will not be seen as much as when you are full bolt on's.  Installing ANY intake without a proper heat shield is actually hurting your performance.



 If you are looking for something to add some rumble, a quality catback of your choice is fine. Most major brands fit well.  Personally a big fan of Cobb, ETS, R400.

IF you change the J-pipe.  Please use a CATTED j-pipe.  The money you are saving could cost you down the road.  ( Reason's why? The stock wastegate and back housing is not capable of controlling boost when the exhaust is allowed to flow.  Your thinking that means more power.. However, the truth is this can push your turbo to a point it's creating to much heat, an uncontrollable boost curve, or push the fuel system past a safe point. With the Cobb DP you will be able to control boost just like the OEM and have safe control. The catted DP works well enough to not hurt your power. Let alone the smell and carbon monoxide risks) NO tuning of catless systems.


Boost Controller:


We suggest the Cobb EBCS, or the grimspeed EBCS.  Always double-check the routing.  When you are considering going to a custom tune is the right time to get one! I highly suggest having one if you're getting pro-tuned. It allows tighter control over the wastegate system. If you're using the GS EBCS we personally upgrade and use a high-quality line.


Intercooler Upgrade: In our opinion, this should be one of the first upgrades you do. The wrx comes with an undersized intercooler stock. Past stock boost levels it struggles to do its job. Curious to see how your's is working?  Pull up the manifold temp on your gauge screen and watch it rise after a pull. The stock ECU pulls out 3* of timing at 104* intake temp.   Personally, I always suggest the FMIC if you're in areas of high heat.  The TMIC can struggle.   However, almost ANY well-known IC upgrade is better than stock.  Cobb, ETS, PRL.


Bypass valve upgrade:  Over time the Cobb has been the clear winner, the newer boombas have been better will report back at a later on how they hold up. So far so good!  The stock one start's to leak right around 20-21 psi pretty good. Upgrading to an aftermarket one creates more tq and is able to hold a better boost curve.


Spark Plugs:


We suggest changing the spark plugs every 30,000 Mile's Use OEM NGK plugs. Gapped to OE spec.  NGK part number ILKAR8H6



AOS/Catch Can. 


 ​This is simple... COBB.. That's it..  Anything else is a science project. This is up there with the inter-cooler in terms of how important. What does it do? From the factory your car vents the engine crankcase pressure and vapor back into the engine. Without getting into why an "Air/oil separator allows this venting to happen, however, it removed the oil and vapor to the best of its ability.  This allows the vacuum on the engine to still do its job!  The result is preventing the oil and vapor from entering the combustion process.  When excessive amounts of oil enter the combustion it can cause detonation which you see as feedback knock, fine knock learning, or dam drops.  Even if you're not modding the car you will want to do this for safety!


  • ACT HDSS - SB11-HDSS rated at 445 ft.lbs

  • ACT XTSS - SB11-XTSS rated at 510 ft.lbs

  • Anything over that should be a twin disc or STi 6 speed swapped IMO. But I can get you a list of the Exedy twin disc

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