RE: nitro is tickin' me off
You might not have the idle screw set properly. Many times people have a good idle, but its set with the linkage holding the throttle open. The problem then, will be when you apply the brakes, or let off real fast, your carb closes, and cuts out. Pull the air filter off, and take a look at the carb. Just make sure that your idle gap isnt closing off throttle, or when brakes are applied.