I moved my last update on this subject to this new post since the investigation took a sharp turn for good last night. Also, since this is my first post, I'm not good mastering the posting skill. That made the thread looks quite messy to read. I hope that this is o.k. with the forum rules.

Anyway, I think that I ruled out the compressor half of the turbo as the cause of the noise. I took another drive this morning and got more precise understanding of the noise behavior. It’s very predictable. I can hear the noise whenever I step on the gas and it stays on until I let go. It might be linked with the turbo gauge as I suggested earlier or with the speed the car is moving. Reving the engine on park does not reproduce the noise. This tells me it’s most likely not the exhaust components. Could it be something loose in the drive train? I need to work on my reverse light switch the next couple days. When I’m under the car, I’ll look for any loose parts again (however I just did this last Saturday).

At this point, I’m quite happy that my turbo is most likely o.k. Only to hope whatever is making the noise isn’t doing major damage. Thank you all for reading and repplying to my post. If you have more suggestions, please do let me know. Erwin

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Exciting report, at least to me! 700
posted by someone claiming to be EYYU (problem login) on Wed Oct 31 18:10 CST 2007 [RELATED]
Sorry if I confused everyone about what I'm trying to do. I'm trying to spin the turbo, and if possible get the needle pass the midpoint. Here is what I found out tonight.

All this afternoon I was trying to figure out a way to test my turbo on park with no avail. After I got home, I took out the intake and output hoses on the turbo, airbox and intercooler.

The first thing I did is to blow compressed air into the intake to see (actually watch it with a telemirror) if the blade spins well. I worked quite well. It spins quite fast and there is no noise which I keeps hearing while driving.

Well, I’m not quite happy with this. I really want to hear it with the engine running above 2K rpm at least to rule out the possibility that the blade is making the noise. Then, with all the air hoses off the car, I started the engine. It starts every time, but only runs a few seconds and dies. Then, I unplugged the AMM and the engine stays running. I looked into the turbo and it spins. When I rev up the engine to over 2K, I still didn’t hear the noise. This tells me that my turbo is probably O.K. However, I still need to figure out what’s making that rattling noise when the turbo gauge needle passes its midpoint, and the loss of power. Could my wastegate somehow stuck half open, still allow the compressor to spin but not enough to make a decent boost? Some parts lose associated with the wastegate to make that rattling sound when the turbo gauge needle passes its midpoint? Any suggestions from the turbo experts? Thanks.
Another question: What drives the little needle on the turbo gauge, the turbo rpm? the engine air pressure? or the power boost in some unit or something else? --- I just found out: it's the intake pressure.


more update 700
posted by someone claiming to be EYYU (problem login) on Wed Oct 31 19:12 CST 2007 [RELATED]

I took off the hose to the TB and put my palm against the incoming air hose from the intercooler, unhooked the AMM, started the engine and slowly rev up the rpm. I feel the are pressure the turbo is pushing, quite strong. I don't have a way to measure the psi. To my limited understanding: more air->more gas injection->more engine power even on park, is this right? Am I missing anything here?