Webelieve

All, I would like to reach out for some mod ideas and info. I purchased the duramax being my first diesel truck of several in the past. I have nothing but positive comments less one. Why does the tailgate only remotely go down and not back up. The guy down the street has something similar and his does both. The dealership rep that sold me the truck was a dip ****** and allowed his lack of knowledge to rush me out the door. I hav recently added running bars/ tint / and two amps ,1 to the stock speakers and 1 to a 12 sub. Fleet W Mac and country never sound better. Like to know the bells and whistles that are hidden within. R-Steve