you may need to recalibrate the ECM for the rev per mile change? (and you can do a lot more!)
for my 03 CVPI i use an SCT Xcalibrator 2 from Blue Oval Chips
http://www.blueovalchips.com/index.php?action=category&id=2
and i saw this other system called 'Sniper' a while back.
http://www.snipertuningsfla.com/SniperProducts.html
you could probably get someone to just 'tune' your ECM rather than buying a programmer, but i'd find someone like Lonnie at BOC that has experience with and is familiar with cars heavier than Mustangs.
"Enlightened statesmen will not always be at the helm" ~ James Madison
