Ill get straight to the point,cleaned my egr valve last week and was surprised to find a coating of what can only be discribed as a black coating of tar substance on the inside of valve, all though i cleaned this all out and the car is running alot better now its just left me a tad concerned because of pictures i seen normally of egr valves coated in soot build up not tar substance .Do i have any thing to worry about cheers dave ...