boost is still hitting 15-20 pounds and staying not just spiking any IDEAS?

[powerwagon]

Ok I've done the research, have double checked the MBC lines, switched boost controllers changed and checked waste gate actuator and the waste gate is opening. But the problem is my boost is still hitting 15-20 pounds and staying not just spiking any IDEAS?!?
Car has stock turbo, was running about 7-10 pounds then one day last week it started doing this. Brand new boost gauge (less than a month old) I have even hooked it back up stock (no MBC) and still running the same.
Thanks Dan

[Type more slowly.]

 

[carsaval]

What turbo are you running stock, or bigger ? and if its not stock if you have a 16g did you get a bigger flappper installed ?

 

[GST with PSI]

What turbo are you running stock, or bigger ? and if its not stock if you have a 16g did you get a bigger flappper installed ?

What??? Do people even read what they type?

Likely cause: Damaged waste gate actuator.

Possible causes: Damaged waste gate/waste gate arm, exhaust restriction, boost gauge malfunction, or possibly turbocharger damage.

Your turbo seems to be suffering form an disfunctional waste gate. How do you know the waste gate is opening? You won't be able to see it open from inside the car, and the car won't build boost sitting in the driveway while your revving the hell out of it with one hand, and scratching your head with the other. You need to confirm your waste gate is actually operating. Take a hand vacuum pump and put about 15 PSI on the waste gate nipple. If you see movement you know your waste gate is operational. Make sure the diaphragm holds pressure. It should hold for a good 5 minutes. Also put 15 inches of vac on your boost gauge to see if it's calibrated correctly.

Use the vacuum pump to keep the waste gate open. Disconnect the actuator from the manifold and put 15-20 PSI on your actuator again, but this time leave it hooked up under the hood. Your waste gate should now always be open. Your turbo should build no to very little boost. If you don't have a vacuum pump you could try to keep the waste gate open with some vise grips(or equivalent) by keeping the actuator arm from being able to close. If your car still builds boost with the waste gate forced open you may have an exhaust restriction. You don't have a cat so cross that one out. Possibly a banana in the tailpipe? If you can't find any of the problems listed above I would pull off the turbo to give the waste gate and ports a close inspection, along with the turbine and compressor wheels. Good luck.