As above, check everything, you can replace a faulty co pot with a potentiometer from the likes of Maplin, i had a spare one from a previous electronics project and used it in an ofab system with no probs. But certainly check all vac pipes first, and put a meter accross the coolant temp sensor and inlet air temp sensor to make sure they have a rsistance of around 2k ohm, open circuit means they are def toast.