I love my Tazer JL, the two main functions I use it for was the speed recalibration, and the Light Show while responding to EMS calls. I have 285 size tires, I selected the 32.9?? Size and my speed was off a bit when compared to a GPS speedo app I down loaded for my phone, I adjusted to 32.6?? And it's dead on now. Unfortunately concerning the Light Show, the Tazer JL I'm sure is set up for LED lighting and I'm it sure works amazing for that application, but unfortunately just doesn't flash the standard non-led lighting bright enough, but at night it works well enough to be seen, and augments my EMS lights well. Anyhow I am very happy with the product, I like the idle increase you can do while winching, and the rock hold feature that locks all 4 brakes seems like a awesome addition, but it's kinda hard to remember how to activate it, but that will come in time, and with use. I am also itching to use the line lock feature. Overall it's a great programmer, and the customer service the Z Automotive provides is fast, responsive and overall amazing.