The emissions holley doesnt surprise me. Probably running off the power valve once you open it up wide enough to get it moving. Any aftermarket carb tuned properly will get decent mileage and not require lean jetting. Also, I think if your little brother is running 2200 CFM on his motor, he's got to be running WOT a Lot, otherwise there is just no reason to have that much carb. And dare I ask, whats a 462 Buick? A 455 bored or stroked?