A good thing to do would be to install a manual boost gauge to double check that you are actually NOT boosting. You can use a vacuum/PSI diagnostic gauge if you have one since it reads vacuum and PSI. You just need a long hose so you can view it from the driver seat while drivng so you can watch the gauge under WOT.
I had a similat problem as you described, I found that the little filter on the end on the BBV solenoid (located in front of BBV vavle) was deterierated and clogged the port it was on. I simply cleaned the end and installed a litttle vacuum 90degree fitting on the end to keep dirt out. Now it boooosssttsssss.
