MAF (Mass Air Flow Sensor) got ya down!?
Just last month I got the CEL and found out that I needed a new MAF. Cleaning it with MAF cleaner didn't seem to work at all. I searched the web and found out that I could use a VW MAF, however I'd have to remove the sensor from the VW MAF Tube and put it in my MAF tube. (VW's intake's are smaller diameter.) Not to mention that the clip wouldn't work with VW's Sensor.
After a little more research, I remembered that 2003-2005 Range Rovers use the same 4.4L BMW M62TU Motor. I called up the Land Rover dealership and asked what the cost would be for their MAF. To my surprise it was about $120 after tax. After inspecting the part, they're both identical, down to the finest detail. Much cheaper than the $480 the BMW dealer quoted me.