On my chevelle it has MSD ignition already hooked up inside of it. And it came with several different chips. It had 3000 5000 6000 6500 7000 and 10000 I think. Now I was told that they adjust the rev limiter, but even with the 10k chip in the car red lines at 6500 and wont go any farther. So I am wondering what these chips do exactly, and since I drive this car daily would I also increase gas mileage plugging in a smaller chip? Ever since I had it I always used the 10000 so I am not sure if it would change gas mileage, or even what it does.