Necessary for the Elise S2 if fitting a catalytic replacement pipe.
The ECU on the Elise S2 has a function that can automatically register a fault if the Lambda sensor is recording incorrect Carbon monoxide/Hydrocarbon levels.
Without a catalytic converter the above readings will be outside the parameter of the pre set fault level, and will then automatically illuminate the MIL light (Maintenance Light) ie the Red light on your Speedo display.
This gadget simply fools the ECU into thinking there is a Catalytic converter still fitted so in turn does not show a fault code and thus does not illuminate the dash light.
** For Off-Road Use Only **