Turbo spins freely but no boost! Options

[celi_6]

Hey guys, I have an issue with my 2nd gen 3sgte motor. I purchased an exhaust manifold from ebay and put it on. I screwed all the nuts and bolts back on but i was missing a nut holding one of the six bolts holding the turbo exhaust housing to the downpipe. I figured that it'll be okay since it looks tight enough. I drove the car for about 4 blocks and i started to lose power, so I decided to go back home. When I got back to my garage, I started to hear knocking noises coming from my engine and it sounded like it was coming from the head. A few days later I went back to start it up, the noise was gone but still no power when accelerating and white smoke comes out from my exhaust when when accelerating. Car starts up perfect, car idles fine, don't hear any boost leak and no smoke coming out from exhaust during idle. Did a compression test and it came out 150 155 155 150, so I assume that head gasket is good. Checked sparks plug and they all look good, no oil. Wastegate acutuator arm is not loose and turbo spins freely with no shaft play. Took apart all IC pipings and reinstall about 4 times to make sure it is not loost or damage.

Here are some more problems I encountered:
1. When i'm in first gear, i floor the car, the boost gauge needle would jump to 0 psi and drops instantly. happens in all gears.
2. Took off the filter by the maf and when i rev, I feel/hear it sucking
3. Don't hear BOV ( vacuum leak?) I have a Greddy BOV
4. Before the car had this problem, during boost, the green LED knock lights would come on but now, it just stays red.

What could be the reason for my car not to boost? Before I installed the new exhaust manifold, car ran great at 14psi.

[95st-celica]

pull your downpipe off....lay your gasket over the downpipe, you will see that there is more metal around the opening of the downpipe that you have to grind out so that it is even with the gasket...the downpipes from ebay have to small of an opening and need to be ground down, they actually hit the wastegate and keep it open....im not saying this is your problem but it defentially well could be