You are correct, the waste gate controlls boost. However if its bad and doesn't open, you can over spool the turbo which creates high charge temps and high drive pressures, along with sky high EGTs. I'm not familiar with the factory intercooled setup, I don't know if you have a boost dump valve built into your manifold or not. My car had a dump valve that would open at around 11 or 12 lbs of boost and relieve manifold pressure back into the intake before the turbo. The boost readings wouldn't get high, however the turbo was screaming fast enough to make 30lbs of boost and with the waste gate staying closed, the drive pressure was super high and at upper RPMs the engine couldn't breath... A higher reading boost gauge would be a good idea.
Jason
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