I'm sure there is a fuse somewhere, but the electrical connections for the rear defog are made thru the struts that hold the rear hatch open. this is why if you buy new struts for that car they will ask you does it have rear defog. the struts you need must have an electrical connecter at the forward end with a wire attached to each strut. go look.
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.
i know the backs are 6x9
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
I use 10W-30
I know mine is on the drivers side there is a door in the kick panel
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.
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.
Inside the alternator.
10w30 motor oil should work nice