Any added power will add additional strain on your transmission. But if you don't drive like a mad man you shouldnt have any issues. I would run it on lower to middle hp settings to give you some added power and fuel economy.
Like Luke said run it on the mid range setting, and you should be fine. SCT is the best Flash-ware software for the powerstroke. Use the tow mode and you should see an increase in economy. Provided you drive sensibly.
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