Most Popular No - Not California Approved for GMC Sierra 3500

Works pretty good. I get a mile to the gallon better. When I tow a 13000 lbs fifth wheel camper it really does a great job. More hp and 1.6 mile to gallon better. Now the truck doesn’t shift gears as much.

Not a huge difference, towing my 28' travel trailer, but I do appreciate the firmer shifts and ability to see more engine parameters on screen. Over all, happy with the product. Easy to install and use.

Just got programmer installed with dash pod, I haven't driven for any amount of time with the programmer running, but the programmer was easy to set up. It has a ton of functions to customize programming, I'm looking forward to using for towing 33 ft fifth wheel. The installation was fairly easy on an 03 GMC Sierra.

It works as promised... our water supply never froze during subfreezing temperatures

I love this product. I can change my truck to have to pull the house down or set it up to Canon Ball Run lol

I bought this after installing 4.56 ring and pinion gears in the front a rear axles in my 02 gmc sierra 1500. Due to differences in where wheel speed data is collected between the front and rear axles you'll get an abs warning light if you make any changes in drivetrain bearing. This unit has the ability to adjust the parameters for tire size and gear ratio in order for the ECU to perform the necessary calculations. The result is that the ECU can then realize that both front and rear wheel are in fact rotating at the same speed, which turns of the abs light. I also used a GPS speedometer and adjusted tire size so that the indicated speed matches perfectly a calibrated gps speed perfectly. Its actually more accurate now then it ever was. So I can confirm that this unit will correct both issues you may have. I havnt used any of the "canned" tunes so no comment on performance, towing or mpg gains. Just adjusted the parameters on the stock tune and been running it like that for a year with no issues

So far I have only used it on the 87 octane tune setting. Definitely an overall mild improvement in performance. Does not kick out of overdrive while in cruise control mode nearly as often. Picked up at least one possibly two miles per gallon.

Easy plug and play 87 octane tune gives better throttle response and shifts reprogrammed the speed limiter a bigger speed on a Chevy Avalanche and it worked perfectly plug and play install took 10 minutes which was mostly running the cable to the OBD port

I love it and the customer service is the best I’ve ever seen