The most important item is the DME report, which will show you range 1-6 over-revs (if any). While looking for a CPO Boxster S for my wife I received 6 different reports because each of them "bombed out". One of the cars appears to have spent most of its time over the rev limiter. Opinions vary, but if you see 4+ ranges, then that indicates possible / probable damage. My feeling was 1 and 2 was acceptable as that will be recorded just if you bounce off the rev limiter. On the one I purchased, I had the DME report made part of the contract documents with a letter from the dealer that in no way was warranty impacted from the few range 1 ignitions recorded (added piece of mind). The issue is that if you buy a car without knowing how the engine was treated and it "dies", then Porsche reads the DME and says "this engine / car was abused, so no warranty..."

Another thing you can do if you are really focused on absolutely knowing the condition of the engine is have an oil sample sent to Blackstone Labs. I think I paid about $75 for an expedited analysis on a 964 I bought a while back. Amazing what you can learn from the oil...

 

Ron, thanks for making it clear on the DME report. I did see a few threads on that and it did get pretty in-depth. Sounds like 1's and 2's are ok, stay away if it shows 4's and above, and 3's is a grey area.