I have an '05 4wd with auto and recently pulled the muffler and cat leaving a straight 4" pipe. That seems to have increased mileage about 10%.

I am considering a power module for the increased fuel economy they advertise. A mild power increase would be welcome, but not a critical concern. What would be the best investment at this point for increasing fuel economy. Smarty? Jr? Other?

 

if you're not looking for a big HP gain, I would look at the Jr. With the REVO & POD you have alot of fine tuning to get the mileage that you're looking for.

If you want to hit over 500Hp, then start with Sr.