A while back, I had my car tuned at BBI.We did a Protomotive flash and set the boost to 1.4 bar.

The car ran 1.4 bar for a long time with no issues.A little while ago, I ran a track day.After that day, the car would only make about 1.0 bar and was very laggy.After some troubleshooting, I realized the issue was related to my old exhaust.I switched out the old Europipe exhaust for a new Fabspeed X pipe setup and the boost problem was fixed…mostly.

The car is now boosting 1.2 bar but still isn’t making the expected 1.3-1.4 bar.I’ve tested the system for boost leaks and there are no leaks.There is no shaft play or wheel issues with the turbos and the wastegates appear to be working fine.I filled up with a full tank of 100 octane to ensure there were no timing issues that would prevent full boost.I replaced the N75 valve and also cleaned the MAF.

The only other thing I can think of is the backpressure difference between my old exhaust vs. the new exhaust is preventing the current setup from hitting 1.4.Any other ideas on what the issue could be?

Here’s the engine setup:

2001 996 Turbo
K16 Billets
997.2 Intercoolers
Protomotive Flash
EVOMS diverters
IPD Plenum

TIA

 

How exactly was the leak test done? A less restrictive exhaust might make more boost not less, especially if you ran 100octane and eliminated knock. Does it still feel laggy? Sounds like a leak still.

 

if as part of your boost leak testing you didn't check the intake check valves, they often can affect - boost and yet go undetected. they are replaceable, cheap items, and are often overlooked as the source of minor leaks, to the consternation of the owner of the leak. this i know.

just a thought, assuming you isolated all the other usual suspected sources of leaks.

 

The leak test was done by removing the lower hose and blocking off and then pressurizing the system with a compressor and measuring the psi the system was holding. It held 15+psi with no sign of leaks. If it had a leak, it would've leaked at a much lower psi.

 

I'm unfamiliar with the intake check valve. Do you have a part number?

 

https://www.6speedonline.com/forums/...6&d=1423832022

https://www.6speedonline.com/forums/...5&d=1423865543

996-110-135-70 is the one to the left of the plenum. the top one i cant find the part number. any porsch parts place or many here can/could help further. but hope this helps somewhat.