Hey Paul,
I remember posting a complaint early days about the throttle being more of an "on - off" switch than a smooth applicant of light throttle power. Herky-jerky at the lightest throttle speeds.
Learned to deal with it over the years - but a LIKE200I is not my fav vehicle in crowded, light throttling city traffic stop and goes 15 feet at a time.
Do not recall any other kinds of roughness.
On a motorcycle I could work the clutch and gas for smooth low speed riding ....but a scooter's centrifical clutch has a mind of its own. It catches, then throttle off, it doesn't.
One can ride the brake I guess to work against things...but I don't.
If this isn't your issue - keep describing so we can throw ideas at it. Like pasta...one of 'em might stick on the wall.
Imho...don't think Dr P's are the fix...but I'm certainly no expert.
Stig