Here's a link to my WP thread over on RennTech:
another water pump story - 996 Series (Carrera, Carrera 4, Carrera 4S, Targa) - RennTech.org Forums
I'm running aftermarkets on both my 986 and 996, and I've had Dex-cool in the 986 for a long time and a lotta miles. The big thing with the WP is to get a plastic impeller and be sure you've flushed any pieces of the old one out.