Originally Posted by jbrady

Actually, the circular LS filter is better than the K&N for this application. The KN has a solid panel in the middle of aound 4" or so in diameter. The accordian element goes around that. The stock filter has a LOT more surface area. Probably filters better also. No need to change filters simply modify the stock air box as shown. I picked up a solid 1/2 MPH in the quarter mile running 5 passes back to back with and without the modification (I have a spare housing cover). 10rwhp is good for about 1 mile per hour so that would be right at 5rwhp. Performance testing back to back in the same environment is the best way to determine actual gains or losses. Actually, you are very hard pressed to feel 5rwhp either way. That said, get 5 here and 10 there and it begins to add up. I just got my headers today and should be picking up another 20rwhp very soon.