Ah, bugger!!

Well the S8 only needs one wire from the lambda and thats the signal wire to pin 2 on the ecu. The sensor itself needs a pos and neg for the heater. As for a 4 wire lambda, the other wire is probably signal ground so just earth it to the other neg wire? You probably need to find out what make your sensor is and do a search for wire colours/jobs. The signal wire off my 3 wire one is white!!!