Can the stock exhaust flow enough to smoothly sustain 17-20 psi of turbo pressure at 5000+ rpm?

I have recently installed a K04-15 and gotten the appropriate K04 GIAC file, but am gettin boost fluctuations above 5000 rpm. I am working with Curry's Auto (the software dealer) to diagnose and resolve the problem.

I have swapped out the N75, replaced the MAF, replaced the coolant temp sensor, replaced my plugs, and replaced the coils with older style bolt on type (a master VW mechanic and enthusiast I know says he believes the older style are much better than the newer push-on type).

I have used Lemmiwinks to turn down the boost to 80% of max (~15 psi) and don't have the same symptoms, but at full boost ~20 psi, boost bleeds off erratically above 5000 rpm.

So...we think it may be an exhaust/back pressure issue.

Any thoughts?

 

Def get a new exhaust, it will open up the full potential of the KO4.

 

yeah when you get a ko4 an exaust upgrade is pretty much a must.

 

+1 the stock exhaust can handle the stock car but once you start pumping more air and fuel through the engine, you need to make it easyre for it to get out. you should also notice a nice jump in powere.

 

i ran stock exhuast -cat with my t3t4 for a while. when i went to my 3" i got ove 40whp gain

 

that sound about right. It like taking a deep breath in then having to exhail it through one of those coffie stir straws.