96 S10 Blazer Vin 4 4 door 4x4 4.3L with 4L60E with 80k on rebuild

The orginal issue was lack of power / lugging / pushing out trany fluid from breather

Got the engine all fixed up (from a nasty P0300) and now what I have is lugging, on brake stands from 500 RPM idel to 1500 RMP (any forward gears and reverse) there is like a tick or knock not paterned just random like every 1.5 to 3 seconds.

When driving it lugs unless I do F.O.T., then it will fly fine til it upshifts into next gear, then back to lugging.

Checked fluid FULL and nice RED color (NOT BURNT)
No signs of leaks (not even from breather tube)
Pan dry, tail shaft dry
No SES lights, No codes on scanner when checked

Any ideas or help would be wonderful

Edit:

Just another thought, the truck has 175k on it, might this be a cause of a failing Timing Chain?
Not to sound dumb, but as they say that only dumb question is the one that you dont ask