I'd try a Superchip or a SCT Excal. I gained a little mileage with these brands when I drove right. No tuner will give you a boost in mpg unless you have a light right foot.A set of electric fans will gain you a couple of mpg.At least they did on my 97 F150. I got 2 mpg better mileage after I put the fans on. Troyer Performance sells a good dual 16 inch set that I used on my truck. You get quicker warmups & better air conditioning with them too.
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2004 F250 XLT crew cab
NRA Life Member
Club SNL Member No.4
Tennessee Chapter Member
Troyer also has a group purchase going on right now with an electric fan kit. They only list 1997-2008 in the purchase post but Mike told me he could cover pretty much any application. My truck picked up about 1 mpg (very good considering I'm running with a supercharger) and about 15 peak HP.
You're going to have to use a chip for your application, not a tuner. It will need custom tuning to address the O2 sensors due to the true duals. Troyer can handle this as well, as can other competent custom tuners if you prefer a local guy.
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-Ken
Look, I'm gonna have to ask you to go ahead, just come back another time. I got a meeting with the Bob's in a couple minutes.