VANOS seals become hard and stop controlling oil flow – symptoms include a loss of power and an engine that “sounds like a bag of nails”
Carbon can build up in the exhaust if the car is driven on many short journeys
Plastic chain tensioners wear out and should be replaced
Each cylinder bank has its own mass airflow (MAF) sensor, which can fail and force the car into “limp home” mode
The idle control valve (ICV) can get clogged up and cause a rough idle; all it needs is a simple cleaning
Oil leaks in general
MY00 and earlier: Oil consumption is normal
The secondary air injection system can get clogged up every few years, and cleaning it is about a $2000 job. There is a mod that stops the ECU from checking the system for problems, and not fixing it doesn’t seem to cause any actual issues.