I have a 2008 4.8L Silverado 4x4 and am looking to mod it a bit, ordering a Gibson exhaust tomorrow and looking for a filter. Is their any difference between just a drop in K and N vs a CAI? $50.00 for a drop in and $300.00+ for a CAI what would be gaining a few hp and .5 MPG more with the CAI? Or is it more drastic then that? I dont care about looks ect I want best performance!