In the search for more economy on my 91T16 ( Lucas EFI with Lambda) I had tested every component and tried every trick I knew but it was stubbornly refusing to cruise as economicaly on the M-way as my old 85T16. Last week I experimented with adjusting the AMM- I increased the resistence of the AMM from 350 to 450 Ohms and have been enjoying much improved MPG since. Throttle response is smoother and less hesitant between gear changes and overall the car feels much nicer to drive. I think it is now running leaner because I get the occasional flash of my knock LED when I hit the accelerator hard - this is just a single flash not a dangerous blinking of constant knock. Also the engine temp is slightly up and above 80mph it does creep up to about 3/4 which is quite hot - another sign of a leaner mixture. This was a slight suprise since I always assumed that the fueling was totaly controled by the lambda in cruise mode (closed loop) but it would confirm that when you go outside the closed loop it uses the AMM signal to derive fueling. I would also assume that adjusting the AMM the other way will increase the mixture if you are boosting higher than stock and want more performance - with 180K miles on the gearbox I'm more interested in economy and drivability (and legal sub 90mph M-way speeds).