Recently installed a Superchip, and K&N CAI, exhaust has been done for awhile on it. The first set of figures as far as mileage goes were not impressive enough to post. But I guess it just need a little time to work the carbon and rest of crap out of the engine. I was getting no better that the equivlant of 13 miles per gallon around town and best on highway was about 16.5. But now that the CAI and superchip have gotten used to thing and my driving style I am get 15.8 around town and 20.4 on the highway. Sorry for all the point 8s and .4s but this is all converted from miles per litre to miles per gallon. Just an added note my truck will break over the 100,000 mile range in about a week or two.
I am reasonable happy at the moment and the big test will come in January when I head south for the winter with my 5th wheel behind the truck. I am not expecting big changes but even 1 or 2 miles per gallon with the trailer on will be a help.