Originally Posted by benzaddict SG

Be careful, it may not be the air pump. I would recommend performing a couple quick checks before you spend the money on the air pump. On a cold start, take the rubber hose off of the air pump and feel the amount of air volume coming out of the pump, they usually either work or they don't-not much grey area. If you have air flow from the pump, then the air passages in the cylinder head are most likely plugged. We are starting to see this quite a bit on high mileage M119 v-8's, where the air injection passages get plugged with soot and gunk just like the EGR tubes, which means the head needs to be removed and cleaned. Not a happy diagnosis if that is your problem, but I'm sure you'd rather know before you spend money on a pump and still have the same problem. Good luck.