It would probably help to know what kind of truck you have. I have a Smarty tuner in my truck, but most of the emissions have been removed. I waited until my truck had about 60,000 miles before I did the tune. I have it on the towing setting and haven't had any problems yet. I don't hot rod the truck though. I can tell you that the oil stays much cleaner now. I would do it all over again.
According the overhead display ( I know its not exact ) I showed 14.5 mpg also pulling a 33' Mountaineer 5th wheel driving about 65 mph.