Have this C5 in with the following fault. Start from cold engine idles for about 30sec then starts to misfire getting progressively worse. Mil flashing and cat fault indication on display. Switch of and restart and invariably it improves.2 faults present p0300/p0302 multi cylinder misfire, misfire cyl 2. Swapped coil pack, same. Does anyone know of a common fault with these? as it could be fuel,ign,mechanical, and i guess the ecu is shutting down relevant injector once it sees misfire. Once the car is warmed up it runs fine with no problems and has just flown through MOT whilst this fault is present.