Intermittent RF Wheel well smoke

[RogerA]

I've got a 2007 2500HD Duramax which occasionally likes to smoke out the RF wheel well, and stinks up the cab.

The smell is a mix of exhaust and diesel fuel and occurs completely at random.

Doesn't matter if the engines hot or cold, its winter or summer.

Sometimes so heavy it looks like the engine is on fire.

As soon as you open the hood the smoke is gone.

I've had several mechanics check it out and even witness the smoke, but no one can find any issues.

Everything is dry under the hood and no obvious fuel or exhaust leaks.

I think I've 'exhausted' my resources.

Thanks