Red,,,
From what you described,,,, it does sound like you have some some sort of air leak,,, or perhaps a leaking check/power valve in the carb,,,,,,, from the description of what you did to the piston and cylinder to remove the aluminum xfer,,,,,,:monkey: some worn out parts with the piston slap/rattling as stated !!!!!!
Just curious,,,,,while you had it torn down did you check/inspect the rod bearings for excessive wear/end play or the crank/bearings/seals for run out/tears????????
Don't let the Stihlheads get you riled,,,,,,,
It does seem strange that one would refuse the friendly offers that others in good faith/kindness have made,,,,,, with good OEM parts,,,,:monkey: that would make it a good runner???????????:monkey:
Hope it all works out for you,,,,,,,