Exhaust odor inside the car when the engine is ideling

The obvious thing to check is the exhaust system to be sure there's no rust holes or other leaks. That really shouldn't be a problem yet on a 2004 model. Check the tail pipe to be sure it didn't hit something and get bent.

The less obvious things are to look for the rubber hose hanging down from the passenger side of the firewall under the hood. That's for the air conditioning condensate drain. The hose is formed to a thin slot on the lower end to reduce air coming in. Also check the rubber weatherstrip along the rear edge of he hood. If it's out of position, air from under the vehicle will be drawn up to the fresh air intake.