Stihl Weedeater Wont Run Full Throttle

[Racanelli]

My Stihl weedeater won't run full throttle. In fact, it won't run at all unless the air filter is off. Do you have any suggestions on how to improve it?

 

[Wildlife]

Check wire screen attach in front of muffler maybe built up with carbon,can wire brush carbon off or replace.