I took mine off thinking more air cooler engine. But after attending the mtg in MI and talking with the engineers about the wind tunnel results. I put them back on. I had noticed getting up to the higher numbers I was taking longer. There is a noticeable difference if you are going to do any half mile or mile events. It does serve to keep the under body streamlined. Take a look under any Mercedes and everything is tucked away nice and flat. That is for the air flow under the car. Do as you wish, mine are on to stay.