Shanin, why the heck is your '07 mileage so low? Sounds like a major issue there (being serious).
Honestly, I am not sure. You would think the exhaust, CIA, and larger tires (PCM was reprogrammed when I got the larger tires) would not effect it much, maybe even help it?
I only drove the truck with stock wheels and tires for 2 days after I got it so I really don't know what the mileage can be, or is suppose to be. I have had it in for recalls and a few issues and I mentioned that to the mechanics and they all tell me it is the large tires. I call BS, but it is really ok. The low mileage is the price I pay for a F/S truck

My next truck will most likely be a Red Ram
The Ram is our road-trip truck! We got 29 mpg when we took it down to Eugene OR and back