lets hope that this is the problem. we will see. Change out you cats and let everyone know. also did anyone else have stock cats when having this problem?

 

i just recently got this problem. a few days ago i had my cracked header (passanger side) replaced from my local shop. also my car before this was running great and made lots of power for NA atleast all the way up. i had some no name brand test pipes on. (non resonated). well while the header replacement i wanted to get some resonated test pipes installed. the shop installed and them and since then i felt this drop in power as i go higher in the RPM range. making the car feel very sluggish uptop. where before my car would start to really move up top now its hesitating in gear. i hoked up the scan tool to the car and get a multiple engine missfire code, this seems very odd that my car would do this now seeing as how i had the non resonated test pipes on my car for almost a year now. i had a check engine light but never a missfire code. any help would be appreciated.

Hammad

 

I have those cats too but when I was NA i didnt throw a p0300.

 

I know the Stillen SC does not like high flow cats or test pipes. I am going to take them off this week.

 

Just to close this out. I put the stock cats back on, gained about 0.5lbs of boost and have not seen the code since.

 

did you gain boost and lose power?

 

I never got a dyno. I doubt there was much change. The plan was to do headers and h/f cats, unichip, injectors, and a smaller pulley to help get the lost boost back.

By the time I add all that up I might as well sell this kit and spend a little more for a set of twins.

 

I have recently had the same problems with my aps tt setup. Rough idle, die whenever I come to a stop but when I plug the stock ecu back in and run that it seems to run fine. I have checked my injectors, replaced plugs, checked for vaccum leaks, etc but still have no clue whats going on? I just sold my unichip thinking there was something wrong with it but I had grd check it out and they said it was fine. I now have the utec and even with the aps tt map from turbo xs it is doing the same thing. I'm starting to think it has something to do with the fuel...
brooke

 

i've got 8.6CR pistons, so really, P0300 is my friend