I run a k&n in my rig and the dealer said i had to switch back to factory filter because the intake is full of gunk from it . this makes me mad im getting 38mpg and know it will go down if i switch. how could the factory oil on the filter make problems for the intake?it says ready out of the box. Was the dealer looking for some work and just saying this? anyway going to continue on with it in there and get another opinion. What you think out there?