I have 1000 miles on my 03 crew cab dually H.O. This is my first cummins and i'd like to upgrade the air box/filter. Also looking into an auxillary overdrive for when I'm not towing (i have 4.10 gears). Anybody out there have a gear vendor to give me the mileage difference driving with/without a gear vendor and using 4.10 gears? (include your cruising speed, rpm, and if u have a trailer or empty). Any reccommendations for airbox/filter upgrade?<br><br>Thanks in advance