I am using the EVO-GMT4 which comes with the T-harness. 2008 2500HD 6.6 Duramax WT with standard key. All programing went fine, after initial installtion had a fuse blow - under hood DIS 2.5A fuse - replaced and system works with 3x lock button on factory remote.
If I key start the truck I get a security light on the dash, stays on solid the entire time. Truck runs fine just has the annyoing light on the dash. Have not pulled the code for the light yet as it goes out if I start with the 3x lock feature.