One thing that will contribute to clogged exh. ports is running a trimmer with the line shield/cutter removed. The longer line slows the engine rpm's and builds up carbon.
If it's just the screens yer talkin' about, just remove em.
" But let me tell you something ,folks: You can't fix stupid!
There's not a pill you can take, there's not a class you can go to. Stupid is forever!"