If you decide to mount one stay above and between 9 and 3 on a clock dial so it will not collect moisture in it. Also make sure it will not collide with anything during sing frame movement. If your only going to use it for the auto tune there is methods and mounts you can use to go up the rear of the pipe just make sure you get up past the cross over on duals to get a accurate reading. any exhaust leaks will add O2 to the pipe and give a false reading. Also some sensors are off calibration when tested against dyno anylizers. I suspect the tuners that use muti spectrum gas anylizers on their dyno's have much more accuracy if you near a dyno shop that knows the power commander gear which is like most of the shops on the planet it might be cheaper to just have them tune it in for you. It might not cost much more then the auto tune unit if any. I am not kicking auto tune but with a dyno the operator can hold and test all throttle percentage areas in each rpm band on the PCV unit where you might go buy a area to quick. The auto tune unit has to take more then one sample in each area. With a eddie current braking system on a dyno this can be done easier.