I can't quite define the smell but exhaust probably comes closest. I don't smell it when moving but when I stop at a light the stink builds up trememdously. I have also recently noticed a big drop in mpg. I've been having this problem for a few months and I recently cleaned my K & N air filters(I use 2 as a replacement for the OEM's) and it has gotten worse. A mechanic friend is suggesting that the air flow sensor might be coated/clogged and is causing a greater fuel consumption. I'm wondering whether the oil spray used on the filters might be causing a greater problem with the sensor. It's about 200 miles since I cleaned the filters. He mentioned that CRC puts out a spray cleaner for the sensor. Any comments would be appreciated and where is the location of the sensor? how do I get to it? As always thanks for any assistance