I have read an old tread that says "did an efi course the other day. the bloke running the show said that ef and au falcons had earth problems. he said that the shoddy earth made the computer think that you were accelerating when you weren't. apparently there is an earth connection in the harness near the ecu. it is covered with purple tape. if you pull off the tape and solder a piece of 6mm wire to it, then earth it to the body, voila ! instant better fuel economy. Can anyone advise is this a worthwhile mod? Or are there any earth mods/upgrades?

I have looked at this and there is a crimp joiner near the ECU connector that begs to be soldered. When I did mine I also moved the earth from the ECU mounting strap screw to its on screw directly on the body. End result Zero.

its not a point of moving the earth. IIRC there are approx 3-4 earth points that join to this one stingy piece of wire and is supposed to be solid ground for the car's electricals so by adding a more appropriate grounding point this rectifies the problem

its a case of cars being designed by engineers and being built by accountants