I have had three types of CAI for the hell of it. First, in a stock truck, they don't increase mpg's and I have hand calc many tanks over the same runs with the same weight and weather conditions, etc.... I was indicating a slight increase at the beginning, but I have tracked every tank from when I bought my truck new. (The first CAI was installed after year 2, so I have a base mpg number to go by.) If I can say there was an increase, it is documented as close to 1 mpg for me.
If you use the stock system, their are two things you can do that will assist in the stock system, but won't increase mpg's. (in fact you will not see the mega mpg increase they advertise) On one of these diesel sites, someone wrote up how to remove the veins from the filter tube to the turbo. It's not that hard. But make sure you do it right and it's clean of all remains of the veins or they can end up in your turbo blades. You can pop an extra hole in the bottom of your housing and install a tube to extend inlet where it gets outside air and not from your engine compartment. Called a HomeDepot addition.
If you go to the oiled air filters, caution of over oiling. Many do and you can unknowingly send the oil to your turbo blades, and when they get enough on them, unbalance the blades and destroy your turbo. Be very careful to oil properly. There are many who believe in them and many that hate them. I don't want to get into that.
I understand, but do not have the specs at the time, that the original air cleaner can handle up to 700 hp. But no one had test results that can prove it to be so, so this is to be considered hear say at this time. But many have maintained the stock box. You have the choice of the stock filter or the 4" filter. Same thing just different debris capacity.
If you want more mpg, maintain your truck properly, like oils, filters, filters and tire pressure. Drive like an old fart. Don't jack rabbit starts off the light, don't race and don't exceed the highway speeds. These are WORK trucks, and not design for eco mpg's of 50+. It's hard, but the truck will shortly get you whatever it wants and your stuck with it. (just don't be shocked at the mpg when you max the bed and trailer weight out for a long run, I was, it was an eye opener. But I still won't go back to a gasser).
