What is this part on my 95 E320 cabriolet?
 

It looks like some underhood air duct. It starts behind the grille in the bumper and ends at the passenger side engine mount (green arrows). It makes no sense why this part is on my car.

That is the air intake. Don't go fording any rivers or moderately deep puddles o you'll suck in water and do some damage.

I can't help you but I was trying to figure out the same thing on my 1995 sedan. It doesn't seem to do anything

It's not connected to the intake. It's open at both ends. I'm either missing some parts or this part is useless and can be removed.

It appears to direct air to the engine mount.

It maybe something that works in conjunction when the underbelly pans are in place.

Seems like it would ram cold air to the mount location which disperses it and hence also cools the pre cats area.. and finally exhaust out from the opening in the pan - Otherwise the only air coming in would be the through the radiator..

This is a cooling duct for the motor mounts, the V8 cars have it to.

WOW - cooling for motor mounts, the diesels shake more but lack them - do the gas cars have the thermostat louvres in the wheel wells to exhaust hot air?

sometimes you wonder what sort of team was working.

Here ve haf kuhl aer for ze motur mount - as hydraulics make heat - ve need to kuhl it viz cold air.

Imagine a guy at the chevy design team saying this and then promptly getting fired :)

OEM motor mounts are fluid filled.