My truck has been on both the Mustang and the Dynojet. Most of my runs on a Mustang. The Mustang seen to be quite good and accurate up to 350-375 HP. Above that the tire slip causing low numbers. I believe the Mustang is a better Dyno for doing R&D work because a set hp load can be put on it so it simulates going down the road better than the Dynojet which is better for high numbers.
At our Utah Dyno days when HebeRam did his NOS run, I was standing just off to the side of his LR tire and I had to wipe off rubber from his like new MTRs off my shirt.
Any place that does emmision test for NOS has a Dyno some are the same Mustangs that we do our testing on...