Wrencher,
If you decide to investigate the chain tensioners ,this may be useful:
http://986forum.com/forums/performance-technical-chat/52043-cam-pre-tensioners-timing.html#post411549
The diagram here may help also:
http://www.pelicanparts.com/techarticles/Boxster_Tech/16-ENGINE-Camshaft_Swap_and_Chain_Tensioner/Gp1800.pdf
But please promise to let us know what the problem was and what fixed it -otherwise it doesn't help us to help others.