UPREV! Others have tried the jet & unichip with lack luster success. You can do the mail in for $300 or get osiris for $700. It will fix the DBW, remove the speed/rev limiter, give you up to 5 maps to choose from, free downloads when you add other mods. Just wait and the Uprev troops will chime in on this and get more specific on what it has done to the performance of there trucks.
Link: http://www.uprev.com/products/products.html
Link: http://www.uprev.com/products/products.html