My saph 4wd cosworth had a knock sensor fitted when I stripped it for the rebuild, obviously I want to put it back the way it should be BUT I'm being advised mine should not ever of had one fitted???

It's a 1991 (J) Red top built in June 1990 and I have it in my hand and it does fit the block and plug in the loom.

Question is.....do I refit new one or bin it??