Okay, so I got this 1987 760 turbo, and I got it into running condition. It's done pretty good, but this weekend I had a spontanious problem. I took it out for a test drive (after swaping the springs/shocks) and it did good until I got to about 20 mph. I noticed a loss of power and it wouldn't go any faster. Also, there was a hissing/high pitched sqeaking noise coming from under the car (or from under the hood, reflecting off the road.) At the same time my trubo gauge was reading low (but that could be due to the poor engine performance.) I've checked all the intake clamps and manifold nuts, and still suspect something in the intake. I'm also gonna do a cat test when I get some dry weather. Does anyone have any idea what I should look at?

Alright, I got a chance to finaly look at the car after the deluge we've been geting since Sunday evening. Turns out I did something wrong when I put my turbo back on. The oil feed line was in the way of the AMM hose, and the clamp wasn't making a good seal.

This sounds like a bad turbo hose. Check all the hoses between the air cleaner and the throttle plate by removing and inspecting them carefully. A hose will leak more under boost conditions because it is pressurized.