larger cams, ported heads, larger valves all to increase the air flow of the engine, tighter piston rings to decrease leak down to keep more of the combustion process efficent. Lighter pistons and rods to reduce drivetrain loss, lighter valve train components to reduce drivetrain loss.... it all ads up. You build a motor properly and you will have a substantial amount of more power than before even if you leave the turbos and boost levels the same.