Sounds like you are dumping boost as soon as you make it. Check to make sure your BCA (boost control actuator) is working properly. Look at it as the engine is running. It is a little canister on the front of the SC. there is a little plunger going to the SC with a lever, it should be in the up position, and move down when you rev it. Here is a pic to show you what it looks like -
What is circled should be sticking straight up, and moving back down onto the stop when revving the car, if not, the BCA is leaky, or you have a faulty vacuum hose, or even a bad BCS (boost control solenoid).