Since it is understood that the 10K mi intervals for oil/filter changes, (per AUDI), is too long and probably, the 20K mi interval for air filter changes is too long, we are you all doing about spark plug intervals? Audi says: 55K mi, but considering the mis-fire issues, (and the resulting expenses), is 25-30K mi, what we really should be changing at? Comments Please, experiences, please...