Stumble/Hesitation on light throttle

On my 750 Mighty Demon annular I have a slight stumble/hesitiation @ 1900 to 2000rpm while cruiseing only with a slight tip into the throttle.

It had factory 31 shooters front and back, I changed the front to a 35 and it seemed to get a bit better. Should I keep going bigger or is there another problem?

The air fuel ratios have been checked while driveign and are all good so I'm not worried about jetting. Vacuum in gear at idle it pulls are 11 - 12" so I have also left the factory 6.5 power valve in it.