Thanks for taking the time to try and help me.
The car has never had any work done to it other than routine services and an exhaust system replacement.
However there is some history leading to this fault which I forgot to mention. From cold the car would start after warming the glow plugs by turning on the ignition 3 times then turn the key all the way to engage the started motor. The car would drive approximately 1/4 mile then cut out, at this stage it would be a devil to restart, when it eventually did restart there would be clouds of black smoke. After this initial problem the car would continue running fine all day, I replaced the heater plugs which did make a difference but not totally solve the problem. The air and fuel filter was changed for new Mitsubishi ones in October last year at the same time I replaced the front seal on the fuel pump as recommended by the guys on the Mitsubishi owners forum. What I did fail to mention was that when I took the fuel pump off I noted that there was heavy oil deposits around the butterfly valves that connect to the Intercooler. Other things I noticed that when sat in the cabin whilst trying to start the car there was some electronic / electrical clicking coming from behind the dash on the left hand side.
I am really scratching my head on this one, I think I have one fault that connects the rev counter to the poor starting and lack of power. But is it 2 unrelated faults that just happened at the same time, I just don't know.
What I have just remembered was that when the fault arose prior to it becoming undriveable my wife had called me saying she had broken down about 20 miles from home, I arrived at the where she had broken down about 40 minutes later and with much swearing got it to restart, when following her home the car would let out a little black puff from the exhaust about every 3 to 5 seconds for the duration of the journey.
The problem as I see it is that the engine does not know where it is as the throttle is either nothing or flat out within a slight amount of depression of the pedal the remainder of the depression has no effect, hence the reason I purchased a new throttle position sensor (£450 quid down the drain). Now the car will start but when you turn it off then it will not restart typically until the next day.
I hope this helps with your diagnosis. I am at the point of scrapping it but it is a super car that is structurally sound and her that must be obeyed insists that I can repair it even though 2 of my local garages have given up. I guess I am hoping you can help pull a rabbit out of a hat or any other such magic trick.