Ever since I purchased my 2005 8 with 24,000 miles (AT), my gas mileage has been horrific. I've been averaging just about 12-13 mpg in the city and around 15 highway. I notice sometimes that after starting up, a weird smell comes in the cabin then goes away after about a minute. Also, sometimes when I throw the car in drive after reversing (or vice-versa) I hear a loud click that sounds like the gears were violently changed. (I come to a complete stop before changing from drive to reverse, vice-versa). And to top it all off, my cabin heater broke.

So, long story short. I took the car to the dealer this morning and am still waiting for a call back from them.

Anyone have any ideas?

I searched and searched for the rotten egg smell here on the forums but I'm not sure how significant the smell has to be in order to signify a bad cat.