2003 Kodiak hesitation

Hi Everyone,

I have a 2003 Kodiak 450 that has a hesitation issue from 1/4 to 1/2 throttle. Past 1/2 the machine runs beautifully
If I add some choke or restrict some air flow into the carb, the machine runs fine in all positions

I, along with another mechanic have gone through carb, valve adjustment, spark, intake leaks.

What else could this issue be as I have exhausted all ideas?

Thanks!

Frank