It is listed in the 1991 Pontiac Firebird Operations Manual
What parts??? Body, engine, suspension???
I calc'ed my '91 V8 Formula Firebird to be about 18 mpg.
A firebird can't "have" third gen. It either is or is not a third generation firebird, and Yes, a 1991 is a third generation.
underneath the drivers door
5x7
I know mine is on the drivers side there is a door in the kick panel
I use 10W-30
I have a 1990 Pontiac firebird, and the gap on that, I believe is .035. If you still have the sticker under your hood with the engine size, it says it right on there.
300 pounds
A wiring diagram, for a 1991 Pontiac Firebird, can be obtained from most General Motors dealerships. The wiring diagram can also be found at most auto-parts stores.
Roughly 4.5 quarts with a filter change.