I did the test with the throttle wide open both hot and cold.I found this table to adjust for altitude when performing compression tests:Altitude Factor1000 .97112000 .94283000 .91514000 .88815000 .86176000 .83597000 .81068000 .7860It looks like a logarithmic curve starting at roughly 3% loss in pressure every 1000'. So at an elevation (5500'), I'd be looking at about a 15% loss. So Ace, what would the procedure be to obtain some power but retain ease of starting? Would I pull the head and barrel, take it to a machine shop to see if it needs a rebore and then order a piston to fit that rebore? Or is that cost the same as ordering a new alloy cylinder and corresponding piston from the start?