After about 5 years of problemless performance, I've got a turbo issue. Let me begin by stating that I am currently running a G-Force ECU and full 3" exhaust @ 1bar of boost. Anyway, I was driving the other night and I noticed that the top end power was lacking. I checked my boost gauge and noticed the following:

The primary turbo came on line with no problem and produced a full 1bar of boost. Then, during the transition, the boost would drop to .5bar and the needle would flutter for about a half a second. Then, as the secondary turbo came on line, the gauge slowly rose but only to about .75bar whereas I usually get a full 1bar at WOT.

Also, before I noticed the way the boost gauge was behaving, I noticed a noise coming from what seemed to be under my car when I was driving. It is extremely hard to explian what the noise was but it was kind of like an intermitent ticking sound. The sound was only produced when I took my foot off the gas while still in gear and the gauge dropping to the lowest point of vacuum (.60hg).

Can anyone give me a place to start or offer any insight into what may be the cause here?

 

I would check the Turbo Contol actuator on the exhaust manifold. It has a c-clip that can come off causing it to kind of "bang around". Not saying this is your exact problem, but it's a good place to start.

 

Thanks Mahjik, I'll check that out. Anything else?