My origional one was in the engine bay just infront of the drivers side fuse box, to the left of the engine mount. It was a square 1" black box.
I put the replacement on the back of the instrument pack. The little black box that's already there is a buzzer I think.
That's not the usual place to wire in a delimiter.
I'd check to make sure the original wiring is all back in it's correct place as that delimitter may have been spliced in-line to wires into the ECU.
Most are fitted behind the speedo as it's easier to break into the signal wires and frees up clutter at the ECU.