Since the needswings is the only true fresh air intake outside of the engine bay, in theory I believe your hp will increase in actual outside conditions. An even greater increase with cold air entering into the filter as you accelerate. That's why it whines when you see them in the vids making wide open throttle runs. It's the air being sucked in from the front of the grill. If you sit in your drive way and rev the rpms, it won't be as evident as driving down the road. Your throttle body can only suck in so much air, at which point it doesn't matter if you have 4 pipes going in. Now someone should try extending one all the way out front and the other in the engine bay and get some results.