2005 sportsman 500 ho

2005 sportsman 500 ho Carb Runs great down low but if held at 3000 rpm it sputters and sounds like it’s hitting the rev limiter but when given more gas picks right up and runs great up top. Carb was cleaned new fuel filter and intake boot, but hasn’t really helped the issue. Any ideas?

The machine in my brother-in-law's but I'm the "chief mechanic" of the family. He had it up north at a hunting property with other side of his family. He went to bring it home around Christmas and it wouldn't start. Got it winched onto the trailer and pushed into my garage. Definitely was...