I have a lack of power at 4000RPM, but the car is running on N/A exaust.
Could it be the problem ?

But the boost is good, 5.5 PSI, heat is good. Everything seam good, but it lack of power at 4000RPM.

 

? any help ?

 

I'll try to answer that

If your using a highmileage OEM exhaust with both OEM cats, that could definitly be an issue.

 

I really dont know, but is the NA and Turbo Exaust are the same ?

Cause "right now" it is NA exaust on MY turboII

 

"exhaust" being catback?.....

that wouldn't do much. I don't think the cat or higher would even bolt up.

 

is it 4000 rpm and up or just at around 4000 rpm? If its just before 4000 rpm and the engine kind of lugs or cuts fuel it is probably the infamous 3800 rpm hesitation which will require further diagnosis on your part.

 

No, its not the INFAMOUS 3800 hesitation.
Anyway, ill put it streigh pipe tomorow to make the test, and if its good, I put the car in the garage, remove the engine, and put it in the Vert.

Btw, im new to the board, ill hook you up with pictures of the project. And, sorry for my real bad english.

 

Check your secondary throttle plates to see if theyr'e opening freely.