Boost leak quandary

[Mark_six]

Hello everyone. My mechanic and I are head scratching so I come to you gents with my situation.
2010 gti
APR STAGE 3, APR DP, intercooler, and k04 kit.
all work done by apr tuner.

im supposed to be putting out 28-30psi on full send. Now my boost is flatlining at 10-11 sometimes only 7 psi. Checked and cleaned air filter. Smoke test showed no leak. Thoughts are: wastegate, dv, or worst case Bad turbo. Any input from y’all who have more under the hood time than I do?

 

[GolNat]

Did you run some logs? Requested vs actual boost? Pressure test the system to see if any leaks occur when you crank up the psi.

 

[Joe_Mama]

Did you check the PCV? If the diaphragm has ripped you won't be able to make boost as your described

 

[Francoleon91]

Did you check the PCV? If the diaphragm has ripped you won't be able to make boost as your described

This isn't true. A ripped diaphragm wouldn't have anything to do with him not seeing the requested boost.

As golnat said, i would pressure the entire system for leaks otherwise it could possibly be a wastegate issue. Theres probably a bad leak that only opens up once you actually hit boost and that wouldnt show up when you smoke test it, thats my guess.

 

[Joe_Mama]

The PCV is under boost and anything under boost can by definition cause his boost levels to lower if it's defective.

 

[Francoleon91]

The PCV is under boost and anything under boost can by definition cause his boost levels to lower if it's defective.

while I agree that the pcv does see boost it still wouldnt make sense to why he is not seeing the requested boost. Think about it. If he is seeing 10-11 psi from his boost reference (boostgauge or AP), he's most likely getting that from the manifold correct? manifold comes before the pcv. Also, I HIGHLY doubt a ripped diaphram would make you lose 15+psi, I've ripped one pretty badly and all i noticed was a semi-rough idle but not any noticeable loss of performance like hes experiencing.

 

[Joe_Mama]

It's not likely you're right but it's still worth checking. With a 10 psi drop it's probably something more serious. Turbo related

 

[Mark_six]

Thanks all. I’ll get back to you with these, been on vacation so just now seeing.