Echo SRM-266 won't rev up

I have an Echo SRM-266 trimmer and it won't rev up. It will run about half throttle; seems like it doesn't have any power. I've changed carburetors, put new fuel lines and filter on it. Put new plug in it, took the muffler loose and it still won't power up. It has 70 lbs. compression. Could a weak coil or air gap be off causing this problem? It sounds fuel related to me but I'm stumped. Could someone offer me some good advice? Thanks in advance to anyone who responds.

Echo SRM-266 won't rev up