Vakari

I know you said theres no overheating in the components but what your describing sounds exactly like what someone may experience when there CPU has to throttle back from too much heat. I would try 2 or 3 monitoring softwares, and do a stress test on the CPU to see if you get consistent thermals across all 2 or 3 tests.

I reinstalled it, screwed it down tighter, that was it, clocking 50 average 70 at max now

Only need to order more if you take it off...
 
check to see if it all the way down