It's an '01 and generally runs great. About 4 years ago upgraded to 4" exhaust thinking mileage wud improve from 18-20. Now its about 17. No other mods except KN air filter. And, its loud in the cab now with that big muffler right underneath. Thinking about going back to stock. Wud a programmer help to mileage sitch? Also, had a limp mode last year while towing a 300lb trailer behind a load of hunt gear in the truck. Changing some older fuel lines and 1.5yr old/7000mile fuel filter solved the prob. Shud I just plan on a filter chan ge at 10k or so?