the gen3 is an interference engine and the ls is not. they can run extreme cam configurations without piston to valve issues. so the can puff the 91 fuel without much trouble. the gen3 has a far more efficent chamber and radical cams come at a radical cost. boost to boost the ls cant touch the gen3 design. its the block decks, open cylinder bottoms of the blocks and heads available that limits the gen3. apachies are worthless under pressure. the worst gen3 heads for boost there is after spike cylinder pressures. they dont have much deck thickness as the rest. eagles are the best bang for the buck. it is what i have going on my current 5.7 build for 1300+rwhp. have yet to decide if ill oring or copper head gasket the heads. seems to be lots of differing opinions on the matter.