Doing a tune up on a 05 750. runs fine at idle then falls off at mid and pulls hard on top. All stock except k&n air filter. Cleaned the carbs, removed juts and blew them out with compressed air and clear to see through them. Guy says it has always been like this since new. Was going to shim the needles but wonder if the shims from a dyno jet kit would work or too thick or thin? The bog gets worse when air box lid off. When i apply a little choke with lid on it goes away.