I had a K&N RE0880 with the red prefilter sock for awhile then pitched it for the Amsoil airbox filter, which I like better. My K&N let too much dirt through, but I think I had a bad one. Others report better filtration and low silicon counts in oil analysis than I did.
As far as the airbox, removing the snorkel between it and the fender is a MUST if you are BOMBed at all. Also drill some holes in the bottom half of the airbox for more flow.
Vaughn
------------------
'01 2500 QC Shortbed 2wd, 6-speed, 3. 54LSD, Cab & Fog lamps, Camper & Tow Pkg.
BOMBed: DD2 Injectors, PS Boost module, Amsoil air filter, straightpiped exh. , Aeroquip 3/8" fuel line w/tank mounted lift pump, AutoMeter Sport Comp gauges, Line-X'd, Amber turn signal conversion.