After owning my 4.0se for the past 3 months and absolutly fantastic as it is, after pulling me off a very stickey rally feild caravan in tow, after taking me 340 miles round trip to my mothers for 10 weekends getting around 25 to the gallon in absolute luxuary and style it starts to give me 10 to the gallon, i found the problem HO2s sensors or actualy a small wire broken going to the multi plug. i have since found out the ECU fuel manegement system takes data from loads of sensors to keep your MPG up, a sensor goes down so dose your MPG . by the way HO2s sensors are just infront of the cats on the exhourst some have one on each some have two. still a nice car would'nt be without it. cheers