OK, so I bought a 2004 WRX and decided to do a few mods. Here they are in order..
1.) HKS Blow Off Valve. (I got this before I heard not to get that first..)
2.) PLX Digital Boost Guage. (Capable of holding up to 200 different mods)
3.) GReddy Ti-C 3″ turbo back exhuast.
4.) AEM Short Ram Intake.
Now when I’m driving it feels like the turbo is hesitating and wants to sort of buck and then kind of go. I’m going to try and explain this part the best I can. When ever I am driving and I switch between 2nd-3rd and then 3rd-4th after pushing in the clutch and lifting my right foot off of the gas naturally as anyone else would, the RPM’s seem to rev up between 400-700 RPM’s from the point where I pushed in the clutch and lifted my foot. Anybody have any information that could possibly help me please!
you need to retune due to the intake which on that car with those mods isn’t worth much power anyway. Its best to retune for every mod you do. It cost a little more but you have the extra insurance of the car running right for what it has done to it.
With what you have, mostly cosmetic (no offense), I would not worry about it just yet. Tunes can get pretty pricey and before you tune you should have a reason to tune. I will not argue that you should tune after any mod. But that is not practical sometimes.
2004 Subaru WRX needs one mod before all others. That is a downpipe. This pipe is very restrictive and can cheaply be replaced $150-$500 with anywhere from 20-80 hp increase. I would reccommend a downpipe with a metal high flow cat in it. The difference in horsepower between a high flow catted downpipe and a catless downpipe is a matter of a couple hp on a car that is pretty much stock.
All that said from what you said about you driving experience I would go for a tune pretty soon. The intake will definitely change how much air (sometimes less that the stock) gets to the engine or the change in the placement of the maf might be screwing up you fuel ratios because your ecu is programs to react to air in a specific way and you have changed the game with out telling it.
My advice, very soon by a downpipe (look on NASIOC.com) and maybe look into an RomRaider or another opensource ecu.
The hesitation you are feeling is due to the BOV. The HKS unit especially is known to cause off throttle issues and also idle issues. The rest of the mods are going to require tuning. 04 and newer ECU’s have a big delay between open loop and closed loop tuning and that down pipe may cause enough of a spike in boost to damage the motor. The intake may cause some AFR changes that can also be harmful but not as big an issue as that down pipe. You really need to at least get some kind of re flash for that or one full throttle pull with the right load conditions and you can blow the engine.
Yes, with the exhaust alone, go to and get an accessport, set it to stage 2.