Some notes based on my experiments with firmware changing. All of them i use.
MembersPage/Andrey/SpeedSensor
My page in Russian http://rus.vems.hu/punbb/index.php
just found iac_freq!=0 with stalled engine and any position, it switch fast from 0 to 100% with unstable freq about 5Hz, but with runing engine all ok.
(it's video - rename to *.3gp