check your ball joints
If there is a clunking noise on a 1991 Firebird Formula 5.0 when going below 30 mph, and the clunking noise does not happen when the clutch is depressed, it is probably a problem with the flywheel. The flywheel moves freely when the clutch is depressed. When the clutch is not depressed, it could be that something is rubbing on the flywheel, like the clutch plate.
usually if it clunks on clutch release its the a frame ball joint on the rear axle
If the disc is installed correctly the clutch will engage and disengage smoothly. In most cases if the disc is installed backwards the clutch disc will bind against the flywheel/crankshaft bolts and not release resulting with a clutch that doesn't disengage. More than likely if the disc was installed backwards the disc is now damaged and will need to be replaced.
No, it sounds like the compressor is failing.
Possibly the clutch was installed facing the wrong way, or the clutch has not had enough time to properly seat.
No, a clutch has nothing to do with effeciency of the engine.
If you have hydraulic clutch there is air in the lines and needs bled. If not hydraulic it could be a stretched cable, a bent clutch fork, or they have installed a clutch for a different model.
I live in Kansas City and paid about $800 for a new clutch, installed, on my 1990 Celica GTS.
It may be as simple as an auto adjustment. If you have installed a new clutch/ clutch cable. If it is auto adj all you have to do is lift UP on the clutch pedal with your foot while driving.
If it was installed properly there is no need to break it in.
there is really no adjustment that can be made, because it is a hydraulic system, the only thing that can be done is to have a new clutch installed.
Clutch release bearing, if installed in this particular Nissan transmission (I don't know the specifics of this particular transmission), probably needs to be replaced. Clutch release bearing, if installed in this particular Nissan transmission (I don't know the specifics of this particular transmission), probably needs to be replaced.