You have tuning problems.
Which advance curve are you using and have you verified that that curve is actually what you are getting?
There is no such thing as a ready-to-run carburetor and tuning is required. I know they will advertise that it is ready to go but it is not. Have you tuned it?
What is your vacuum at idle?
Different gears can help but it is probably not your problem. What is the current gear ratio?
Lawrenceville, GA