Update.
I can feel a bottle of champers coming on, but I won't push it just yet.
Found out where that ticking was coming from, this time I was better prepared and had a long screwdriver with me so I could pin point where the sound was coming from and I did.
Problem is I don't know what this part is or what it does, but I will try to describe it. (Part No. 001 140 99 60)
It's black, made of plastic, has the words MOT and Motor embossed on it with an arrow pointing out the direction of air flow, about 3" in height, has two rubber pipes connected to it which supplies air, is also wired up with a two pin plug, has a rubber ring around it to secure it to a metal hook and it's just under the Brake ABS Unit.
On closer examination I tried to unplug the cable, it was so difficult I had to carefully prise it off with a screwdriver. The two connections were very badly corroded and were obviously causing a very poor connection for the electric current. I also pulled the rubber pipes off then decided to start the engine just to see what would happen. The engine was misfiring and the tick over was all over the place.
Cleaned the connections and WD40d them, put it all back together and took the car for a test drive. Lets put it this way, I thought the car was quite powerful when I first bought it but when I put my foot down "HOLY C**P", my teeth almost ended up in the back of my throat.
I'm going to MB tomorrow to see if I can get this part replaced in case it has been damaged in anyway.
Even though I have replaced the Air Recirculation Flap (which I soon found out did not cure the kompressor problem) and even though the part is on loan have decided to keep it just to be on the safe side.
Any ideas what this part is and what it does, I will be very interested to find out.
BigD