my car also has the same inlet, definitely S2 as it isnt the 2 piece S1 style, and it looks identical to a normal S2 inlet, except it has no knock sensor, and the inlet doesnt even have a boss cast there, its just non existent

as to what age etc, i couldnt say, as mine is a converted 1.3 pop, but all i know is the inlet is 100% S2, just pre knock sensor.

saying that though, my loom came from the same car, and the loom also has no knock sensor connection, thus why i didnt have an issue leaving it unattached