I just found this programmer for the Duramax engine... here's what they say about it on atsdiesel.com.....

http://www.atsdiesel.com/products/pr...owermodule.asp

Xcelerator™ Power Programmer
The Xcelerator is a hand held programmer which is designed to outperform and outpower other programmers on the market with a power increase of approx. 205rwhp & 400lbft! By plugging into the OBD II port (located under the dash inside the truck) and following the on-screen directions you can perform speedometer corrections, speed limiter removal, and gain amazing performance. Additionally, the Xcelerator retains the stock programming in memory so that your truck can be returned to the original settings if so desired. The Xcelerator has the ability to read and clear data trouble codes (DTC) output by the OEM computer through the OBD II port.

Here's a link to the dyno graphs they showed with this kit....if this is for real I want one.

http://www.atsdiesel.com/products/Xc...or_dyno-A1.asp