Compression readings at higher altitude will be effected just like vacuum readings. At his elevation of 4600' the compression readings will be about 12% lower than at sea level. So if compression at sea level was 170lbs times a correction factor of .88 for the higher elevation, the readings would come in at 149 lbs. I'd say his compression is fine. Looking back at the threads the only things that chaged in the engine is the cam (which wasn't enough of a change to make any difference), and the dished pistons (but his compression readings are more than adequate for the motor to run. I'd still leaning toward something being installed wrong during the rebuild, like cam timing or vacuum leak.