That's similar to what mine was doing after I put in my thrasher. I took it for a spin with it hooked up to the wastegate solenoid as normal, and for some reason it overboosted to around 20 + psi. It felt like it was falling out or missing, then I heard it knock and I got off the gas immediately.
Couple days later, removed the line from the solenoid, and just put the hose onto my bleeder valve. Went down the road with it closed and it built no more then 13 psi of boost. Then I kept pulling over, cracking it little by little. Adjusted it up to about 19 psi, and the funny thing is with a valve (insead of solenoid w/ the chip controlling boost) it'll stay at around 19 pounds through 3rd gear I think. It seemed to run fine at 19 psi with 94 octane and the Thrasher 92. I just have bad fuel pressure, since I'm using the stock reg, and an old pump.
While I'm at it. What are the easiest or surest ways of checking for a blown head gasket, other then oil in the antifreeze. If I let the car idle until it heats up a while, would I see a lot of steam? I dont want to go out and thrash on it to check. That overboosting and nasty knock got me worried, and I wanna make sure I didnt pop one. Reason being, because after I got back from the second blast down the road playing with the valve, when I pulled in the driveway and came to a stop, I pulled the hood latch and saw a bit of smoke/steam come from under the hood. I almost pissed my pants. But after I opened the hood and let it run a while, I saw no trace of it. So I'm not sure. ~
