I would definitely agree with every one's thoughts thus far. I would say there is a speed suffer built in, and that non stock tires or tire wear can account for some loss as well. I would also second the Vapor setup. I have one on my DRZ and it is wonderful. You can add in a heat sensor as well to get an actual engine temp. I'm not sure if they would approve but you could alternatively tap a hole and put the liquid sensor in it to get an oil temp.