This thread is extremly intresting.
I have a dynojet bench but for bikes and we run a lot of bikes every single week in it.
We are having the same problem as we seem to have here! A few dealers close to us are always dyno the bike with 10-20hp more than we do.
So we took one of our Yamaha R1 and had that done in 5 differnt dealers dynojet and 4 of us showed more or less the exact same hp BUT one showed 15hp more than any of us.
And later it was proved he did manipulate the figures BUT the funny thing is that people still go to him and get their bikes tuned since they get a higher Hp! We have runned so manybikes from this tuner in our Dynojet and they always comes out with a LOT less Hp than on his dyno.
So it is easy to mainpulate the hp figures in any dyno and I think we all need to remember that we can just use the dynos as a guidline. If you want to see the before and after dyno from parts you need to use the same dyno and condition. So many variables that can make it go up or down.
But at least all could agree on showing dynos base on the same correcton factor so at least this is a fair comparison.