Can you identify this part?

Maybe wrong subforum but I had parts shops unable to identify this:
http://imgur.com/G7KhQ

Sitting on top of the engine, under the air filter. Diesel engine. 1981 Cadillac Eldorado 5.7 but the engine is not stock (shop couldn't even tell me what the engine was lol)

I just need to know exactly what the part in the picture is.

Thanks!

It looks like a thermo ported vacuum switch.
What needs a vacuum switch at a certain Temp?
Follow the vacuum hoses.

I will make a diagram of the vacuum hoses and report back what I find. Thanks for the help!

Looks like an air pump to me.

this is part of the govenor im not sure the exact name but it controls fuel flow through the fuel distributor pump if you buy a rebuilt pump its usualy pre instaled and adjusted at base calibration find an oldschool parts house and ask for a fuel distributor pump if they have books you may have better luck or ask old guy in a good auto shop may be able to help good luck