Looking at zephyr's picture look at the oil filler cap. You see the cam cover with two ridges going back either side of the BMW name plate. M44 is twin cam 16 valve.
The M43 is single cam, 8 valve, so only has one ridge.
Sorry I'm late to the party on this one but this discussion has taken place before.
There is no second sensor on the UK 1998 M44. If you insert a UK 98 VIN into real.oem the number 9 on the diagram is faded out to indicate not fitted on this model, although the picture is there. Also it is not included in parts list. See extract below.
Being a long time M44 owner I can also confirm it was not on the original that I removed. HTH