I doubt your later model would have the tap. It appears to be something Nissan added to the early GUs and was actioned by the mixer flap - the flap that controls how much air goes through the heater core.
Most info I’ve read isn’t very accurate about when the tap was discontinued.
If you get a mirror and torch you can easily see what you have.
Couple of not very good pics here to show the heater box with and without the tap. In the pic with the tap you can see the rod that connects to the pivot of the mixer flap and you can see the mixer flap slightly open
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