So I dyno'd my stock 1M today and came up with some impressive results (especially for a Mustang Dynamometer) that I thought I'd share.
I did 2 runs while monitoring AFR/boost manifold pressure. The first run was without the M-button pressed. The second run was with the M-button pressed. As you can see both runs are nearly identical hp/tq/AFR/PSI wise, so I think that's a bit more evidence that the M-button is good for gaining up throttle and little more. Another interesting note was that the shop owner recently tested a stock 335is on the same dyno and was shocked to see that I made 40 whp more than the other car. The assumption was that the two tunes were exactly alike... I guess not.
For those too lazy to look at the graph: 340 whp and 400 lb/ft were the average of the 2 runs with peak boost of 12.6 PSI and min/max AFR of 11.5/18.9.