Porsche MA1 / 9A1

The flat-six that replaced the M96/M97 — direct-injected, with the intermediate shaft removed entirely and the camshafts driven directly from the crankshaft. That single change eliminated the IMS bearing failure that dominates its predecessor's reputation.

That is the most useful thing to know about it, because IMS material dominates any search for a Porsche flat-six problem and none of it applies here. Confirming which engine a 997 has — the earlier 997.1 uses M97, the later 997.2 uses 9A1 — changes the whole risk picture of the car.

The 9A1's own themes are ordinary for a modern direct-injection engine: intake-valve carbon at mileage, high-pressure fuel-pump wear, and on the turbocharged versions the usual dependence on oil condition. Bore scoring persisted as a much-reduced concern on some versions rather than disappearing outright.