1. 1Cylinder bore scoring is the defining reliability concern on the naturally aspirated 997.1: the 3.6 and 3.8 M96/M97 engines can score their bores, signalled by a cold-start ticking noise and sooty exhaust tips, and there is no mileage at which the risk fully disappears (Lokasil-block cars are described as more susceptible). Cold-start it, listen for ticking and check the exhaust tips before buying.
2. 2IMS (intermediate-shaft) bearing: the 997.1 moved to a larger, non-serviceable single-row bearing. Failure incidence is markedly lower than the 996/early-997 units but not zero, and because it is non-serviceable it can't be swapped in isolation — many owners have a ceramic-hybrid replacement fitted during a clutch job as insurance.
3. 3Rear main seal (RMS) leaks are far less common than on the 996 thanks to an updated PTFE seal, but still confirm there's no weeping at the bell-housing when the clutch is out.
4. 4NHTSA recall 06V008000 covers the 2005–2006 Carrera S and Carrera S Cabriolet (about 5,094 cars): an under-dimensioned tailpipe seam weld that, if it failed, could let the exhaust pipe detach. The fix was a new longer-weld tailpipe — verify it was carried out on an affected car.

• 06V0080002005–2006
  Under-dimensioned tailpipe seam weld could fail and let the exhaust pipe detach.

US NHTSA campaigns for this model. A listed campaign may not apply to a particular car, and may already have been remedied — check a specific car by VIN at nhtsa.gov/recalls.