Looking for some help with a Holley 770 truck avenger on my mild 440 , 4spd in a Ramcharger. Starts, idles great. Runs really strong off idle, feels like I could burn my tires off my wheels if I wanted too, but as the rpms come up ( I don't have my tach hooked up but about 2500-3500 rpms) engine goes flat with a little stumble and no matter how much more I press the gas it will not rev anymore. As Holley tech support has recommended I've tried different secondary springs and different PV's 2.5, 6.5, 8.5 all with little to no difference. I have other carbs (Holley and edelbrock) all work fine, so I don't think its a ignition issue. Anyone have any idea what else I can try, before I pull this thing and turn it into an expensive paperweight.?