I really don't think that you can expect alot of improvement with gas engines with chips and/or tuners. I have seen some material on the affect of tuners specifically on gas engines and from what I can recall the tuner companies that were used in the article were more conservative of mpg gains then they were with their diesel counterparts, but it also depends a great deal on what Chance was saying on how heavy your foot is. I think diesel's have a much better chance of mpg improvements, but I don't know much about their affect on gas engines, I've always had diesels, I've seen personally a gain(basing it off the computer on my messenger center in the truck) of 3.7 mpg over what I was getting from my previous diesel truck and I didn't have any performance additions in that one.
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