The TRE is a device which allows much better throttle response in the first 4 gears on EFI sportbikes. What the motorcycle manufacturers have done is make a separate ignition map for each gear. This has been done for either safety and/or emissions reasons. However, it limits the power and smoothness of your bike in the first half-turn of the throttle in gears 1 through 4. The motorcyclemanufacturers were clever in the design of the stock timing retard: It still allows full timing at full throttle. As you shift up through the gears, the amount of throttle needed to access the advance curve decreases, until you make it to 5th gear and then it's gone - you have nice, smooth operation. The TRE makes your motorcycle respond just as smoothly in the lower gears.
Quick facts about the TRE: