I’m obviously no expert, so I apologize beforehand if my suggestion reflects that, but we had a very evil throttle response issue on a Junior with the Evo kit. Swapping to a different Evo carb fixed it, after fiddling with settings to no end. So you might not want to rule out that possibility and swap to a different carb (if you have access to it) just to see. Maxspeed accepted the bad carb as a warranty return.
Luis