It sounds like you have a potentially serious issue. Until you find out what is going on I would avoid loading the engine hard (boosting or WOT).
With any issue you should always start with the basics:
1. Vac or boost leaks, this is most common and would fit some of your description. You can build a simple boost leak check system from home depot parts. Do a search for ways to do this. Go around and check all of your hose clamps, FMIC systems are notorious for having loose clamps. Visually inspect the boost system, look for wet spots, look for holes in your FMIC.
2. Check to see if your BPV is leaking or open. You can do this a few different ways. An easy method would be to remove the recirc hose, block it with something like a D cell(the hose on the intake side) battery and then do the boost leak check.
3. Clean your MAF sensor.
4. Some logs at idle and during cruise could be helpful. Look for big fuel trims on both short and long trims of more than +-8%. A screen shot from learningview.exe would tell me a lot if you could post one of them, you will need a tactrix cable.
5. Other issues could be bad front O2 sensor, bad fuel pres regulator, fuel supply problem, bad injector, etc.
The best thing to do is start with the basics as I said. My money (only a wild guess) would be on an intake leak causing a vac or boost leak.
Feel free to bounce back what you find.
P3 Import Autowerks 907.355.6655
Originally Posted by HonduhPowa
I have a 2004 Wrx with the following: ej257 sti block, wrx heads, Atp Garret gt3076r turbo, deastchwerks 850cc injectors, 1 step colrder plugs, hallman pro mbc, turboxsfmic, perrin big maf intake, perrin 3" turbo inlet, forge recirculated bpv.
The car was tuned at Pure Tuning in Toledo, Oh. I have the receipt from the rpevious owner for it.
-Stumbly idle, jumps and falls when cold, and when its warm it sounds like its cammed.
-Very stumbly and jolty when shifting between gears, bucks the whole car.
-Difficult to rev the engine, sounds/feels like it chokes fuel or something when revving and falls hard.
-Revs fall hard when coming to a stop, has actually stalled quite a few times.
Seems great in boost, boost is 20psi (has failsafe in the tune at 22psi). Previous owner said it made 351whp and 331trq, i ran a 12.7@109 as it sits.