Chainsaw Repair

When my friend brought me this saw, he said he could not get it to run. I checked it over, good compression, getting fuel, no spark. I found the two piece ignition modual at ChainSawr. Got it, installed it, now it has spark. It then started, but it ran lean. I pulled the carb & rebuilt it, replacing the welsh plugs & diaphram/gaskets. Carb was clean! It still ran lean, almost to the point of running away to high speed. I pulled most everything apart again & found a previous person had not got the manifold back in place on a prior repair attemt. The manifold had also been damaged in the attempt. Back to ChainSawr & got a used manifold. Installed it & it starts & runs, but only from mid range to top end?! When rpm's get below midrange it dies. If I hit the throttle it takes off again. If the rpm's get to low it will stop &be wery hard to start. If I shoot a little (mixed) gas in the carb it starts & it does the same thing again. The impulse line has been replaced. It does have some scoring on the exaust side of the piston, none on the intake. Any ideas? 

I agree sounds like low compression to me as well. Had a Stihl saw with a scored exhaust side of the piston do the same thing you are talking about. Ran great on top but would die on the return to idle and be hard to start.

Seems low to me I would like to see at least 150