For about 3 months now I've had just 2 k&N filters for my intake system. Everything else was just sucking and blowing ambient air. Now I'm getting ready to sell the car I decided to put the stock air box back on. So thus, all of the acv hose, air pump hose etc.....lines are all connected back up to the stock airbox. Now why would I notice an increase in performance by doing this. it is a considerable notice also. Does anyone have an explanation for this? I figured I would be running quicker without the box, but not in my case. Does it have something to do with the ACV?