as far as i know it is just a switch that deciphers if youre in neutral or not, (though dont quote me as im no mechanic).
If you turn on your heat switch and then put gearstick in 1st gear, the revs will drop to idle.
In my case, 3rd and 4th were giving me grief.
If i put it in 3rd or 4th the revs would not drop. I concluded that this was coz the switch was not functioning correctly and thought it was still in neutral, therefore im guessing the turbo was not spinning and therefore lack of power.
when i took the switch off, it all worked fine apart from the heat switch, obviously.
hope this helps a bit.
