Not sure which 2003 GMC Sierra Power Programmers & Performance Tuners are right for you? We have over 5642 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:
"I was very impressed with the Edge CTS Programmer when I installed it in my vehicle. This along with a K&N Cold Air Intake has increased my gas mileage from 12.5 to 18!! I will also be purchasing the extendable camera that fits with this model programmer.
Overall, I would rate the product a 4.5 out of 5!" —William C B from Dallas, TX bought an Edge CTS Evolution Programmer for a 2003 GMC Sierra, 5.3L V8.
"The DIABLOSPORT INTUNE is a great purchase. I do see a difference in my truck and do recommend it too others. I would like to have more variety of tunes though. Other than that, it gives no problems and does great." —Denny S from Denair, CA bought a DiabloSport inTune I-1000 Tuner for a 2003 GMC Sierra, 5.3L V8.
"Programmer was easy to install takes about 3-4 min power you can feel when on freeway but dont feel in low end tourque. shift point much firmer. still waiting to see my gas milage go up other reviews say gas milage went up with performance tune to 16-17 mpg but still reads 15.1 AVERAGE mpg maybe 87 tune will do the trick." —Pat S from Santa Cruz, CA bought a Superchips Cortex Programmer for a 2003 GMC Sierra, 5.3L V8.
"My truck has the 6.0L and is a 4X4. I was averaging 11 MPG and after installation my mileage increased to 12.5 to 13 MPG, providing I keep my foot off the floor. I anticipate my highway mileage increase above 13. As expected the torque and power increased significantly. Hypertech's tech support was extremely helpful in answering questions GM dealers could not." —R K H from Carrollton, TX bought a Hypertech Max Energy Programmer for a 2003 GMC Sierra, 6.0L V8.
"When I first installed the Performance level program I took a 1/4 mile drive on a straight road out of my neighborhood and didn't really feel a difference down or back. The next morning on the way to work I truly got to test what this thing can do and I was BLOWN away. The pull from 20-80 is nothing short of amazing in all types of traffic. On top of that I am somehow getting almost 3 MPG more. WTF?" —Robert P from Waxhaw, NC bought a Superchips Cortex Programmer for a 2003 GMC Sierra, 5.3L V8.
"First the cortex is easy to install program. I installed the fuel saver program and have gotten around 4 to 5 MPG more on the road. As far as power, plenty of that, at first I didn't think it was up but believe me it was there. I also tow a 14,000 LB 5th wheel I went from 10.5 to 15 mpg in tow mode. Not bad. I'm happy with the Cortex but think there could be a few more programs to chose from." —William K from Franklinville, NJ bought a Superchips Cortex Programmer for a 2003 GMC Sierra, 6.6L Duramax.
"Matched it it up with a K&N FIPK. Having trouble keeping my foot off the accelerator." —Chad R from Orlando, FL bought a Hypertech Max Energy Programmer for a 2003 GMC Sierra.
"lots of power on performance setting... Economy just seems to adjust shift points but did see 1 mpg improvemnet." —Joel R from Everett, WA bought a Superchips Cortex Programmer for a 2003 GMC Sierra.
"I'm from sinking spring pa, I ordered the cts on Thursday and received it Friday afternoon. Definitely great shipping. Installation was very easy, had a slight problem getting it to program my truck but called tech support and they instructed me very clearly what to do, followed their instructions and plugged unit back into my truck, followed the prompts and within minutes I was on the road. I currently keep it on the third power level, 18mpg round town, and pushing 24mpg highway" —Matt F from Sinking Spring, PA bought an Edge CTS Evolution Programmer for a 2003 GMC Sierra, Automatic, 6.6L Duramax.
"I really thought there would more to using this product, but it's very simple and the instructions book is very helpful as well, if you even need it. My truck definetely runs much better now, the throttle feels better off the start and when on the Interstate it seems to keep speed much easier without having to change gears much. The transmission shifts much better and more aggressive when the throttle is wide open. The only thing I've noticed, is the oil pressure is little higher than normal, especially when in higher revs. But all-in-all, great product. I but an AEM cold -air intake on at the same time. They are a great match." —Blair H from Flowery Branch, GA bought a Jet Performance Programmer for a 2003 GMC Sierra.