It's a performance chip. Have heard about them but, never actually saw one or had any exp with them. It reprograms the computer for more perf. Usually, there is a piece of gray or silver tape covering that port.

Kind of like the prom's in the chevys.However, as it rides "piggyback", I would think that it acts like your home comp where it will look to that port first for programming but if it fiinds nothing there, it reverts back to the "default settings" which would be the factory programming.