Hey you guys im driving a 97 A4 1.8T and i just put my boost gaudge in and im only showing about 4 to 4 1/2 psi spike and its drops to about 2 pounds at high rpms...i know it should rund near 6 or 7 pounds . Im pretty sure all my connections are air tight , could i just have a tired turbo ?? another thing is i noticed there is oil residue in the turbo inlet hose,and off the top of my bypass vavle i actualy see a little got to the tube to my gaudge is that normal ?

 

Your psi reading might be a limp mode, do you have a CEL? (sometimes limp mode doesn't cause a CEL but a DTC is present when the car is scanned). You could do a boost leak test, here is a link to an easy DIY kit.
http://www.audigeeks.com/forums/index.php?topic=2034.0
http://www.audigeeks.com/forums/index.php?topic=2139.0
The oil residue is normal, I get a bit of oil in my intake as well (probably just a bit of blow by through the crank vent system).

 

That's a lot of work to find a boost leak. I use ether or carb cleaner to find boost leaks and vacuum leaks. Just spay the mist on the hose/hoses presumed to have a leak with the engine running and if the rpm decreases or the car dies you have found a leak.

 

I had a boost leak once that was caused by a slipped hose clamp. Everything was sealed tight up to 10psi of boost, the air started leaking out at 10psi (I could hear the woosh under the hood as soon as the gauge would hit 10psi). There is no way I could have found it without introducing at least 10-15psi ofpressure into the intake.