funny noise
 

I noticed a funny noise on my 1988 930 turbo cab. When I press on the gas quickly I hear a sharp noise (sounds almost like a light rap on the intercooler with a screwdriver). Very brief and does not affect the car in any manner. The sound only occurs if I goose the throttle. On a more gentle throttle advance it's perfect. No noise. Any ideas? Performance, Temp., oil pressure and level OK. No leaks, idles fine. Thanks in advance.

pop off valve is clacking.

Pretty normal.

AFJ