Significant number of engine failures due to cracked or slipped cylinder liners
Slipped sleeve or "D-chunk" failures did not occur until the late '98 to '99 models when Porsche ran out of cases and re-sleeved ones they had previously rejected, due to poor casting; you should not see an issue with a '97.
Pay careful attention to the maintenance records, especially oil change intervals. Data suggests frequent changes have helped minimize failures over the extended change intervals Porsche was recommending at the time.
I do not pretend to be an expert; they reside at
www.lnegineering.com and
www.flat6innnovations.com where there is plenty of good reading.
Good luck if you purchase the car...they are a blast to drive!