Get a fault code reader hooked up to the car before you start throwing money at it, the ETM is frail and could be on it's way out but the fault could be down to a whole host of other reasons (air leak on the inlet manifold/ associated pipework, Throttle pedal position transmitter etc).
As you know how to take the ETM off the car I would suggest you contact the chap who can repair them (as he is local-ish) see
Here - Mike