Gas and mileage can make a difference, I agree. Anyway, stock torque is really very high, almost every stock 1M dynoed showed more than 570nm or 420lb ft, this means that there is much more than a slight massage to the regular N54 and I now started to think that they put some hp and torque on top of even the Z4 35is version of the N54T which we were expected to believe that is the same engine with the 1M's. In fact, this just makes sense. Since the beginning, I found it suspicious that the M engineers wouldn't go as much as they could (keeping in mind the reliability of the engine and capacity of the chassis and tires of course).
Thanks Chris, enjoy the car and tell us more when you can about your impressions with the car after the tune.
And if you already did not do this mode, try the car with some better rubber, I really feel sorry for those rear Michelin PS2s, they were meant to take care of the "mere" 400 nm of the M3 and only after very high revs.