Exhaust Smell inside

[dan~]

Another little problem here, which would be good to know if anyone else knows wha it could be.

When I was changing my air filter a few months back I noticed I could smell the same smell in the air filter box.

If I'm in traffic and have my fan set to econ, I get a faintish smell of emissions and soon as I drive it goes away.

Any ideas what it could be? Could just be other car fumes, but not sure why the smell is persistant in my airbox