Down on power and apparently running rich would suggest something restricting the engine’s breathing.
By the tail pipe there are several small (maybe 8mm) bolts. Those allow you to pull the spark arrestor screen to inspect it/brush off any built up carbon that might restrict it.
I’d also check/clean the air filter, and make sure it isn’t over saturated with oil.
680 Camo Rincon, Warn XT30, ATV Guru bumper, Mad Dog bag.
500 Foreman, Warn 2.5.
Rides in 30' Patio Hauler 5th wheel. Towed by 3500 SRW Ram.