Rtv excessive black smoke and loss if speed

A couple weeks back I picked up a used RTV 900, 920 hours on it. Its also much louder than my other RTV 900 and puffs black smoke upon start up and also when drive around. I searched these forums for a week or so and have done everything I’ve read and could think of. All new filters, oil, cleaned out fuel tank checked intake, remove spark arrester, cleaned out the muffler. Still black smoke and speed still limited. Engine bogs down at 3/4 or more throttle untill i pull back and engine rpms climb again. What now

Rtv excessive black smoke and loss if speed