A popular mod to get a couple more HP out of M5's is to remove the charcoal filter that vaguely restricts a little air from the engine. I opted to skip that. However the air here in SF is so bad that I can’t see SF from the bridge above it half the time.
After this clears up I'll be replacing those filters and getting an oil change just because. However does anyone know what this poor air quality actually does to an engine -- if anything?