First off i get **** millage 13-16 and it doesn't matter how you drive. I've had tanks at 70 mph, 80-90 mph, all city, pulling boats, it just don't matter. The read out will say 15 -22 but is never close to being correct.


So today I replaced the muffler and cat with a straight through 4in muffler(still very quiet). Leaving the shop I laid down a steady stream of smoke, at normal get on the highway speed. I also notice that I could goose it and produce some smoke. Then still on my way home I stop at a light, when the light turns green i give it maybe 1/2 throttle to get over and the small car disappears in a cloud of smoke.

Now after making it home, I unload the **** out of the bed and take off for a drive. I stand on the throttle... not much smoke, down shift from slow roll... not much smoke. No matter what I do, not much smoke.

Did the truck reprogram its self? Is the lack of cat lowering boost levels? Why is the 07 getting so much fuel? maybe to make up for the power robbing cat?