1992 Saturn SL2 I'm not sure if this is electrical or maech

I have a 92 saturn SL2 dohc automatic. When I put the car into reverse it clunks while i am backing up. Also when driving the car the tachometer fluctuates without revving of the actual engine only the gauge tidals. I replaced the MAP sensor about 2 months ago when it was doing this before and it stopped until now, except then it would die after the gauge went crazy (although it would start right back up) . I just replaced the transmission and the engine was replaced about a year ago. I am getting 3 codes from the car: code 26 Quad Driver Module faulty, code 32: EGR malfunction and code 52: (tranny code) Hold mode stuck on. I have been told that code 26 is common and that it usually leads to EGR valve being replaced however I do not know if this is associated with my symptoms...could it be a bad PCM?