Good evening, this is my first post, but I read all the time on here. I was wanting to put a programmer (think i am saying this write) in my 08 GMC 2500. I tow a 35' 5th wheel and I am only trying to improve my MPG. I get 14-15 around town, 19-20 highway, and 9.5-10 towing (I have been playing with different driving techniques and additives that is the best towing. One thing i did find out by mistake, do not tow with out being in tow mode, MPG went to under 8). Anyways I was at my dealer last week, they sell a couple of brands, and asked them about warranty issues. The service manager informed me that about 30 days ago GM issued a bulliten, that for any driveability problems that you bring your vehicle in for, they are requried to check your ECM for software changes. He also told me that they have hidden a number in their, so even if you swap your program in and out, they can tell. Once that number shows a change, your warranty is done. Is this true? And if so any suggestions? I am going to AR in June with the camper, and of course would like to help my cost.

Thanks in advance,
Bob