Reprogrammed my Yukon XL with my old Superchips programmer. I have had it for 12 yrs just sitting around and to be honest, I forgot about it. Used to use it on a 97 truck I had. I was needing to correct my speedometer and it hit me that I had it and it would do it, so I went ahead and used the 87 octane program. At 75 it is reading 72-73 so I'm calling that good. I need that little buffer zone.