@cwescapexlt4x4
Big Picture : Sounds like you're sucking in oil fumes through your HVAC inlet, which is usually situated at the base of the windshield, on the passenger side.
Suggest checking subsystems that are oil fed (i.e. Turbo Bearings) and located directly around the high heat areas of the exhaust manifolds, starting with the passenger side.
If you don't find anything on the passenger side, move over to the drivers side.
If all seems well in those areas, start looking at the aluminum areas of the intake manifold area.
NOTE: Think about it - It'll take quite some time to see a weeping/slow drip situation on a 6 quart dipstick.
So with that said, I'm not surprised to read that you feel you don't have a leak, but when you smell oil, you have a leak.
It's just enough of a leak that you only smell it when you're idling at a stop light.
The fumes build up under the hood, the radiator ran kicks in, and air gets blown back towards the base of the windshield, HVAC sucks in the fumes...
Good luck!