fuel quantity actuator ???wot is it ???

300tdi auto ,1996 ,this only started today ,seems like only half the throtle is working .you have to push hard down and rearly work it .very very slow to pull away ,no power ,engine check light flashes on / off ,, had it on a fault reader ,says code 0136 ,fuel quantity actuator ,spoke to dennis landrover in aylesbury they have never hurd of it ,just spoke to a guy who works on them alot he to has never hurd of it ,so please could anyone help me out ,thankyou ,