it shouldn't affect mpg as the cams are just causing the cylinders to fire in a different pattern and cause the lope. Unlike the tune that is dumping unburnt gas and messing with the timing tables to cause the pretend lope. That is why Bama doesn't offer it for cars with cats as it dumps a lot of unburnt fuel down the exhaust and could damage stock cats.
I say could as it may not, but there is a chance. I think a few of the other places will write the tunes if you have cats.
Il look into it as well power of google when I'm home later
Any kind of aftermarket camshaft that causes an engine to naturally lope at idle, will impair gas mileage to an extent. The reason for "lope" is the intake and exhaust valves temporarily being opened at the same time. This isn't efficient at low RPM's and results in a lower dynamic compression. However, if the same pattern continues at higher RPM's, the extra valve overlap becomes efficient for making power, since intake velocity is increased at high RPM's.
Our Bama Cam tune simply takes advantage of the 4v 5.0's variable valve timing. We're able to increase the valve over lap at idle, by choice, even though it's less efficient. With the extra valve overlap and lowered dynamic compression, torque is drastically decreased. So, by making only the low RPM's or idle very rich, we're able to increase torque and make the vehicles drivable, without a rich WOT. Thus, we require a catless mid-pipe for our Bama Cam tunes. Which, is the similar technique that is used for aftermarket camshafts with a naturally lopey/rough idle.
This should save you some time google searching! Let me know if you have other questions!
Shane