Really don't think it would change the dyno cause the bikes not moving and forcing air in on a dyno but on the street I'm sure it might of dropped a little.THe reason why you dont see anything like that is cause it restricts the ram air. I bet if you dyno that bike, you'll lose a lil bit of power. The only thing i see it good for is for fuel savings. I figure, less air going in, the less fuel the injectors spit out. But thats just a theory.