Holley 4779 750dp question
Let me approach this from a different angle. You keep jetting it up because you get a surge at light throttle cruise, but adding jet doesn't do anything. Would the rpm's happen to be in the 1800-2200 range when it happens? Also, as for the stumble, does it occur when leaving a stop light (like as soon as you touch the pedal), or at light cruise speeds? Anytime you take your foot off the gas and try to accelerate again (like taking your foot off the gas to go down a hill, then getting back in it to go up the next hill), does it stumble? We're talking less than 10% throttle here.
What are your idle mixture screws set at? Did you set the idle with a vacuum gauge?
Have you messed with the pump cams or anything to do with the accelerator pump arm adjustment?