white/ gray residue in exhaust tips?

i was wondering if any of you that have the magnaflow catback get this?

i thought that it was just from the packing of the magnaflow mufflers, but they have been on for over a year now and i still get this. it appears to be white inside the tip, then when whiped off it turns dark grey. what is this? does it even have to do with the magnaflows or is somthing wrong?

well dark is normal, the reason i was asking is because it is a thin white paste like film?