I have had hit and miss luck with Seafoam and other additives.
I call BS on blaming CARB/EPA for carburetors NOT being rebuildable. Carburetors kits are available on eBay as are new carburetors. $600 to install a NEW carburetor is close to robbery in my book. They figure if you can afford the rig, you can afford the repair bill
I have torn down and cleaned many small engine carburetors, 4 in the past 2 weeks ! If you are careful and don't ruin any gaskets, NO REBUILD KIT IS REQUIRED !
If you suspect bad fuel, before reinstalling a fresh carburetor, empty the tank, rinse with fresh fuel and install a new fuel filter.
Get me the EXACT model number and I will bet I can find a kit/gaskets.