Here is my point of view and it's not because I still own a 335. The N54 engine is bulletproof compared to many other engines and by engine I exclude what I define as auxiliary components like turbos, wastegates etc. So to me engine are the internals, cylinders, valves, heads etc only. Weaknesses on the turbos, wastegates are really easy to fix. If that car was 400 lbs lighter, I'd keep it!
SB, Terra, 6MT. Only a few mods here and there.....nothing extreme!