very odd situation/driving
 

hello, I have been searching/in the garage looking off and on for the past 3 weeks with no avail. my 05 STi was was pretty modded and recently took it back to stock. I still have an APS 3.5TBE, 255 Walbro, one step colder plugs, and BOV on the car yet.. everytime (not just once in a while) I drive the car it sputters and loses revs, let it idle for a few seconds and comes out of it.. once in a while a P0171 will come up, did a boost leak down test and found a few but no more boost leaks and still happening.. when I drive it sometimes it seems fine untill 0psi. than spits and sputters and will NOT rev any higher (almost like an ignition cut out on Launch control), SOMETIMES it will rev to 0psi than I can ease it into possitive boost (and when that happens, sometimes the BOV will release, and other times not, when I back off in boost)... the throttle is sluggish. just thought it was strange to rev to 0psi than really start spitting/sputtering till I ease off throttle than smoothens out.....

almost TOO much of a cut out to be a leaky exhuast.
maybe a bad injector,? but wouldn't that cause missfires.?
fuel pump? but work to exactally 0psi and than cut out.? eh..

I'm all out of idea's. any help would be GREATLY appreciated~~!
thanks guys

MAF sensor. Check it and clean it. If no luck, take it to a reputable shop. The 171 code is a tricky one. I would suspect a bad MAF sensor before anything else with those specific syptoms.

your car sounds very similar to what my car is experiencing, did you ever find out what was wrong with it?