OK, then the ECU must know the following.
Engine speed, which is a given.
What gear the box is in and which way the driver is shifting.
Must be programmed to account for ratio change to know how many RPM to put on the engine.
Graham, are you sure the radical system does not quickly, and briefly, disengage the clutch while its doing this?
Don't know about the Busa box, but the Sadev for sure does not have a "neutral" between gears to alow for a blip.
I suppose a very precisely timed blip could occur just after the lower gear is engaged, but that would also rrequire the ECU to know exactly where the gearlever is during the change in order to get the timing right.
I do know from experience that the Sadev will not change down if the clutch is engaged and there is any throttle on.
Maybe the geartronics system includes this function?
Even if it does, is it worth 4K just to acheive a throttle blip?
Again, suggest you talk to Steve at SWR, he will explain all in great detail.
James, when are you planning to do this? I would be happy to demonstrate the box in my car, but that would probably not be posssible untill next April due to shipping back to Dubai and back to UK again.