main reason that i asked to use the larger filter (the one that was supplied with my CES CAI) is that the CES intake is 3" and the filter is also 3" im just thinking that having a smaller filter would hinder the top end performance of the CES CAI, this is where it picks up over the TRD CAI, this is the only reason that i asked if i could supply the 3" K&N filter for all the tests.