I was lean prior to 740s (dw555s) however and had similar problems with cold bucking but no throttle dip. Messing with my head. Going to check for a leaky injector for the 1000th time. One thing I read yesterday after tokyo's recommendation was that unsynced tb's can result in a bucking when cruising around at low speeds on and off throttle. Definitely try that takes 10 minutes after you find guide.