Umm.in the software.

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I'm very happy with mine as well, but I have not heard of (or experienced) an electronic throttle delay. Do you mean a lack of response caused by drive by wire, or are you referring to the tip-in? If you were an early adopter, there may be a newer firmware available. I'd heard they were shipping a small chip to upgrade early boxes for a nominal fee. Might want to check with BT if applicable.

Set at 100% from day one, I've had one limp mode experience at WOT during the first week. Simply restarted the engine and it was gone. Cleared codes using the BT cable, and no codes since then. Runs like a scalded a$$ ape.

Its the electronic throttle. Better in DS.

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Since this is plugged in under the hood, do you remove it when you take your car in for service? I would think if the BMW Service techs saw it they might not be too happy. I like the idea of this tho...

I would recommend removing it. Mine is tucked under the engine cover, so they should not have any reason to spot it. But why take a chance? It only takes about 5 minutes to install/uninstall it.

Gasoline engines have throttle bodies since they operate at an air:fuel ratio of about 14.7:1. If the air intake in a spark ignition engine were not controlled by a TB, pinging and pre-detonation would occur.

Diesel engines have very large air:fuel ratios as high as 200:1 so there is no need to have a butterfly to control air intake...hence no throttle body to control in a diesel.

Whatever problem you may be describing may have to do with other aspects of the M57, but I don't believe it has anything to do with the "electronic throttle."

OK, let me clarify, since you are making an assumption that I don't understand modern diesels. I never stated that the M57 has a throttle body or butterfly in the system (although some diesel pickups do..)
Throttle response in this vehicle starts at the electronic pedal (Throttle Position Sensor) this signal goes to the DME, the DME then decides on the timing and duration necessary from the injectors. The DME also sends a signal to the Fuel Control Actuator on the injection pump, this ramps rail pressure. The MAP and Rail Pressure sensors provide a feedback loop and the DME does all the magic.
In the pickup diesel world, where I make my living, we call the speed and ramp rate that the DME delivers "Torque Management". By modifying signals, we can change Torque Management, thereby making the truck more responsive. This is normally a function of timing and low load fueling.
I am assuming that the BMW DME has some sort of delay built into it to, perhaps, to save transmissions from being nailed with a ton of instant torque. I have found with other gas BMWs, with drive by wire systems, that this delay exists also. In those cases the motor opening the TB takes some time, but I imagine that he processing loop may have something to do with it also.

Also, FYI, modern diesels run at somewhere in the 18 (low smoke/emissions) and -40 (cruise):1 ratio for AFR.

JB is a very good tune, stable and solid performance gain