I was wondering. My car has been running pretty rich for a while now. Rich enough to turn my tips black within a matter of 2 to 3 days and it gets maybe 250 miles to a topped off tank. I'm possitive I don't have a vaccume leak and my EGR system is all good. I have 2 auxillary emissions control codes and I was wondering if it was the 2 rear o2 sensors because I do nat have any cats. 2.5 to 3 inch back to 2.5 split. Any suggestions? Thanks.