No Particular Order, YMMV:
1. Rust
2. Thermal Reactors
3. Dilavar Head Studs
4. 5 Blade Fans
5. Air Cooled Engines w/o Auxiliary Oil Coolers
6. 964 Dual Distributor Belts
7. 964 Heads without Head Gaskets
8. Early Pneumatic Strut Suspensions
9. Early 928 Vacuum Operated Door Locks
10. 914's (Sorry, I just had to
)
11. 924's
12. Cayennes