I just bought a 99 gmc sierra its the newer body style and has the 5.3l in it, it has 6in susp lift with 315 (35in) tires. The speed o is off about 15 mph and i know that you can adjust that with the programer and do some other tweeking but the motor has 103000mi and some of my friends said that they herd horrer storys of people tweeking high milage engines and having problems with them. has anyone done this or what are your thoughts

 

Ive never heard of this before. Some of its in how there treated to begin with. Theres normally three options on these programmers like performance, tow/haul, and maybe normal or economy. Theres no reason using a controller like hypertech or superchips would cause any thing like what your friends have heard. Ive got 150k on my 6.0L and im just waiting for the extra money to by one for mine.

 

I'd suggest a custom tune from PCM4LESS or nelson performance. They're made just for your application and give you more power.

 

I put a Hypertech on my '02 1500. Definite gains in HP, slight (1 mpg) fuel gain, and most noticable was the torque. I tuned it for running 93 Octane (not real cost-effective, but I figure at the end of the month, it's costing me about $15-20, and we spend more than that on dinner!). I'm very happy with it, and especially enjoy that I can remove/change programming at any time....also helps w/ OBD II trouble codes. Just my opinion....