Can anyone shed any light as to why my 108cdi displays all the traits of a vehicle with a spud up it's exhaust. half the time it's perfectly ok but at times it will only rev up to 3000 revs. My mechanic thinks it is an electrical fault and has so far charged me £50 just for that information, before I take it to an auto electrics specialist I'd like to know if anyone has a similar complaint and how to rectify