Originally Posted by faz

These types of items are usually a simple resistor that replaces a certain sensor's feedback. For example, in motorcycling world, most of the new bikes have a timing retard built into them that usually only works in lower gears ( to comply with noise/pollution regulations), so a 'timing retard eliminator' or a TRE can be installed that takes care of that problem. The TRE is either a resistor or simply a short circuit to ground, depending on the bike/etc.