The gear, and the carburetor maybe the vacuum. i never see a car with so many pipe under hood. is look like water irrigation sistem. the rpm is not stady and few guys told me not to try to fix the vacuum or the carburetor is too old.
Never buy a car older than 5 yrs or more than 50k miles!
I don't know how stupid of a comment that is there are many good cars that are older than 5 years and over 50,000km, why do you think there are so many on the road. How ignorant can you be.