2001 deville. While driving, when driver is down there is a strong smell of exhaust, but not when any other window is open?

 

Any smell of exhaust means there is an exhaust leak. Sounds like it is right near the engine, since it is wafting near the front. If there is a hole in the exhaust below the car, that should be easy to repair. But, if it is near the engine, it might require moving the engine to get to it.

TS