I blew out the master cylinder seals on my GT when I accidentally tried to start out with the parking brake on. I replaced it with a used one that I had on hand from another 85 Fiero. It shifts okay until the car has run on the highway and g, then after a few miles it becomes very hard to shift and the clutch pedal has to be all the way on the floor. Is this air still in the lines or a shot clutch master or slave? Thanks

IF you can pump rapidly on the clutch pedal and improve the dis-engagement point.....there is air in the line.

Ok that's it then, thanks.