I'm just letting everyone know that I'm very very happy with my disco at the moment
I have power I haven't experienced before, smoothness I haven't experienced before, better acceleration response, better gear changes and I now have a system whereby I have a modular Pierburg/Bosch solution that apparently lasts longer (so I have read).
Here's the info to fix your D2 MAF (ie rough idling and loss in fuel economy):
1) Purchase a Pierburg MAF Sensor. Part Number: 7.22684.07.0
2) Purchase a Bosch Intake Air Temperature Sensor (IAT). Part Number 0 280 130 085. This uses the same thermistor as the original Bosch MAF sensor.
3) Purchase a connector for the Bosch IAT. In Australia; ACA Part Number: BK402, Bosch Part Number 1 237 000 036 (I purchased an ACA connector).
4) Remove the existing Bosch MAF Sensor, take you anger out on it and then throw it in the bin. You will need a hollow security torx bit for the screws.
5) Mount the Bosch IAT Sensor into the MAF housing. Details:
i) Relative to the centre of the original sensor, you need to be at least 60 degrees away due to a ridge on the Pierburg MAF Sensor. Mark a line that is in parallel with the airflow. I mounted the IAT so it sits pretty well vertial in the MAF housing after it's all put back together. Don't mount it too far so the IAT connector wires don't reach the original MAF harness.
ii) With a small drill bit come in 4mm from the ridge closest to the engine and make a mark with it by spinning it in your hand. Info:
Engine _____| |_______________________| |_____Air Cleaner
Ignore the dots as I needed to use these to line everything up.
iii) Mark another hole, 15mm from the first hole and closer to the Air Cleaner (this is for the securing screw)
iv) Drill a SMALL hole at both points (about 1.5mm)
v) With a small cone shaped grinder on a drill, remove part of the ridge near the small hole closest to the ridge (as indicated above). You want to drill a hole slightly larger that the diameter of the IAT and you need to get rid of most of this ridge so that your original centre point doesn't move. The diameter of the IAT is 12.5mm, so you probably want to drill a 10-12mm hole.
vi) Drill a hole so it PARTLY goes into the ridge.
vii) Use a round file and file the hole out so the IAT fits TIGHTLY into the hole. Be VERY careful here as a couple of quick agressive files and you can get rid of a lot of plastic and stuff up your MAF housing. I left about 1mm of the ridge in place for support when the IAT was screwed in place.
viii) Find three washers (or one) that is the height of the ridge (about 3-4mm).
ix) Fit the IAT into the MAF housing and use a screw with a wide spiral (for plastic) and secure the IAT in place.
6) Use the same cone shaped grinder (or file) and shave off the outside square edge of the Pierbug sensor as this needs to be round like the Bosch sensor. After you're ground off the edge, check to make sure it fits with the MAF harness connector going to the ECU.
7) Screw the Pierburb sensor into the MAF housing and take note of the arrows indicating the flow of air (look from the top as they are there). Make sure they are in the same direction as the MAF housing arrows.
8) Wire the IAT connector that you purchased in item 3) above. Details:
i) Cut the wire on the original MAF harness that goes to pin 1 (mine was green) as close as you want to the actual connector. Remove around 10mm of the plastic.
ii) Cut 10mm from the red wire on the IAT connector (from 3 above), twist this together with the wire you just cut and then solder it and tape it up.
iii) Get a razor blade or equivalent and cut a 10mm gap into the wire connected to pin 3. Cut it at around 30mm from the connector. Be VERY CAREFUL not to cut all or any of the wires. You need to remove all the plastic in a 10mm area. Once you have done this, twist the black wire from the IAT connector onto this and then solder it and then tape it.
Plug your newly spliced IAT connector onto your new IAT sensor and the original MAF connector onto the Pierburg sensor and you have a brand new hybrid system that kicks ass.
Total cost to me, including delivery etc: AU$201.26 (US$145)
The last decent milage I got was 635km to the tank (120 litre). I'll let you know if there's any improvement from fitting this system.
I don't think I've forgotten anything.