Recently purchased a 2007 RS4 B7. Car is amazing and ran well on the test drives etc. Filled the car up with normal unleaded not concentrating and after quarter of a tank the car has started misfiring and hesitate in the low rev ranged until warmed up. The car has an APR stage 1 remap so guessing this requires a 98/99 octane fuel?Hoping it is just the fuel, possibly plugs. Coilpacks easy to do on these?