Last week we noticed a horrible smell in our 2003 325xi. We thought a dead animal was under the hood or in the trunk. We found nothing. Yesterday my husband took out the back seat. On the bottom of the seat, where there is foam, there are dark brown patches that are the source of the smell! It is awful. Does anyone have any idea what this could be? Is there a way to have the foam under the seats removed and replaced? Help- I am miserable!