First I have seen it.
Post your location and maybe you can stir up some local help. Diagnostic tools are a big help, but they don't solve all problems or even locate all of them. I just sold my Hammer to a guy, and his car has no detectable problems, everything passes the Hammer testing.
For something low cost I think I would look for a tool that originated and is supported within the 928 community like the ones from JDS or Theo.
www.jdsporsche.com
http://jenniskens.livedsl.nl/diag/Diag.htm