You will need that additional sensor. The one pictured is your oil pressure sensor. Remove that blanking plug and whack the new sensor right there. You will have to string a new wire from the sensor through the oil/water pump, up through the front timing chest and to the connector located under the tank on the right hand side. It is a single wire but does not just go straight to the gage, as the factory does it, at least.
Yes, you have the petrol level gage already. Now, there is a small, roundish plug that clips to the side of the 'computer' under the seat. In it there are four colour-coded wires. One of these is the lead for the petrol gage. I think it is the yellow/white wire. Of course there is an earth, or ground wire, and also the hot wire for the gage's power, as well as for internal lighting. Perhaps the easiest way to wire them in is to purchase the factory auxiliary gage harness from BMW. I will look for a part number for you.
Last edited by Two Wheels Better on Tue Mar 08, 2011 7:30 pm; edited 1 time in total