When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Since you have an 03' I'd go with the Diablosport Predator. It is is a very versatile tuner with lots of features. I tuned my dads 03' a few days ago and it is a nice unit and works well.
My first pick would be the SCT SF 9415B I have on my 04' but that unit is only available for 04'-06' SDs off the shelf. The SF 9400 blank tuner can be custom tailored by a dealer to work with an 03' however.
Never heard a bad thing about the SCT but the price is up there. I have the diablo sport and I am very happy with it. I had a superchips on another truck but the diablo has way more options and the power difference was greater. By the way I got my diablo from autoanything for 280. If you call and talk to them sometimes they will give you a better deal than is listed because they work off comission.
Anyone with comments or first hand knowledge on the Hypertech Max Energy Power Programmer??? Thinking of getting this Programmer for my 2000 Superduty V-10. Sure would like to hear from anyone in the know.