I have installed a 770 Truck avenger Holley carb on a mild 440 that I take to the dunes and desert. Seems to run great until about 3/4 throttle, I don't have a tach so I am not sure the rpms but it pulls hard until then, then just quits. Holley tech had me go up a couple sizes in primary jets but made no difference. Now they suggest changing power valve. Seems like I am getting wild guesses from them, so I thought Id post here and get some other ideas first.