01TRANSAM11

2001 Trans Am manual 6 with 98,000 miles. Stock clutch, just installed a MGW short shifter with a new bronze bushing, and had a new GM master cylinder put on about 1,000 miles ago. My problem I have is that it is hard as hell to get the car into gear at times, especially reverse! Other times it is fine. This happens with the car running. Occasionally I will here a squeeking sound while the clutch pedal is pushed in. My guess is the clutch is not fully disengaging? Maybe the slave needs replaced, or possibly the GM masters just suck that badly? Ongoing problem that the garage keeps playing off as nothing. Just had the transmission fluid changed as well. Any thoughts or ideas will be greatly appreciated.