Porsche Repair: 944 turbo boost, roland roland, turbo boost

Question
My 1986 944 turbo intermittently does not booste the normal 1.7+- bar when driving.I just replaced the diverter boost valve. This didn't correct it. They are sending another unit in case the first was defective. What else could cause this no turbo boost?
Thanks, Roland  

Answer
Roland, this is a bit far afield from my expertise, but I did a bit of checking...apparently the exhaust wastegate (or exhaust bypass) is controlled by a spring loaded actuator...and its linkage can sometimes be at fault.  Beyond this, I'd have to defer to the folks who are helping you.

Dave