I have had the AGR valve changed on my 1.8 FocusTDCI about 3 month ago. The car was down on power and putting lots of black smoke out the back. This stopped the fault but now its back again lots of black smoke and down on power. I hope its not the AGR valve again.What I would like to know is this a common fault with the TDCI Focus. If so what can I do about it as I do not wount to spend £ 400 + again.