Hi, my 2004 2.0 16 valve C5 Auto (gas converted) (80,000 miles) had the anti-pollution light problem with no performance problems, however on a run out one evening the car just started running really rough (felt like only 2 or 3 cylinders were firing! The car was telling me there was a cat fault, however on inspection the cat appeared fine the matrix still in place, the garage initially thought the timing belt had slipped but that was fine then they suggested that the drive plate had cracked or the crank had gone so they took the gearbox out but found no problems! Now they are saying it's the ECU? (not a citroen garage) So i had a chat with Citroen at Small heath Birmingham and the tech was saying something about fluid and filters and it would cost between £6 or £700 quid to sort? Does the petrol engined model have the same system as a hdi? I am confused to say the least, I know the cold start air injection pump is faulty but surely that wouldn't cause a severe malfunction would it? You cant run the engine to run a diagnostic so the garage is struggling, I don't particularly want to spend a grand to sort it on top off what I have amounted so far, any ideas please? Mart