Are all the cars running low boost actually making 250bhp?? Loads of variables though to be fair, spec of turbo/head and the engine in general, and as you say setup especially on efi where you can maximize the efficiency of everything. There is a point, especially where turbo's are concerned that you can wind the boost up and make little or no difference in bhp, maybe a bit more torque and i'm sure some people just run as much boost as the turbo will make in the hope of squeezing out a bit more bhp.