I can vouch for them too, on my 2012, his tune was by far the best.... Tune, off road x pipe and stock everything else, car went back to back 12.40's at 114.$$
They do and they stack on top of the tune so your results may very. It's one of the reasons I'm staying away from a tune for now until the tuners have more control over the new Mustang ECU. I would like them to be able to make adjustments to every mode.
Rev Auto just got a '15 A6 Eco that is about to get testing on so dyno tunes will be available soon over there. They already do very well with the M6's.