I have a 2002 325i that runs great but has an unusual rough idle only on cold starts. When I start the car in the morning, it idles higher and I hear the secondary air pump working, but when it starts to idle lower the engine shudders for a few seconds and then smooths out. There are no codes being thrown and the engine performs great in every other aspect. Is this normal? Is this just because the secondary air pump is injecting air into the system. Just curious if this is normal.