Without getting into atmospheric pressure, coanda effect, and other such scientific things associated with the large air pumps we use I'll throw in my .02 cents. Point it whichever way you want, you'll feel no difference in power. Nor is there and actual difference in power output. You don't drive fast enough to create a high enough pressure zone to boost power. And there is no air pressure drop with it on backwards to reduce power. Some guys turn it backward to reduce the chance of something flying into the intake i.e. hats, sunglasses, beer, water, hair etc....