Steve Weiner-Rennsport Systems

Not really; I've seen guide issues in engines with as little as 3K all the way to 60K. IMHO, a lot of these problems are due to loose guides right from the factory.

Since the 3.6's have hard-chrome plated valve stems, we mostly see wear on the high mileage (80K+) engines.

pp000830

I have had this intermittent experience on both my 930 and my 993. My guess is it could just be some dirt or deposits on one of the valves or the edge of a worn belt slapping around. Put a couple treatments with Techron in you gas and see if it quiets things down. Don't look for love in the wrong places as this can become an expensive and unnecessary date.
Andy