http://www.tuneruniversity.com/blog/2012/07/whats-so-wrong-with-nitrous/ "The danger with nitrous, is the same as a turbocharger or supercharger, if you pack way too much air/oxygen in with not enough fuel, temperatures can sore inside the cylinder and cause components to melt/warp. To avoid that problem, we simply make absolutely sure that the air/fuel mixture is relatively rich (lots of fuel to keep things cool) and we do everything we can to avoid pre-ignition by running conservative ignition timing of either stock values or slightly “retarded” values." There goes your mileage. you would need to run rich all the time unless you program a stand-alone fuel pressure controller.