Not sure which 2003 GMC Sierra Performance Chips & Programmers are right for you? We have over 7429 customer reviews, with an average rating of 4.5, to help you find exactly what you're looking for. Here's what some of our customers have said:
"Shipping was fast and installing was super easy. Put it in a 03 gmc 2500 hd. I had moderate gains on mid engine tune and havent tryed the performance yet. Transmission shifts are alot stronger and might be getting about 3/4 mpg better. Display is nice with lots of different choices on colors. I havent tryed towing with it yet but it is worth the buy." —Todd C from Saint Albans, VT bought a Bully Dog Triple Dog GT Tuner (49-State Legal) for a 2003 GMC Sierra, 2500HD, 6.0L V8.