where does this hose go? (pic)
 

1988 300E

Off of the black breather hose coming out of the air cleaner there appears to be a small line that looks like a vacuum line. Unfortunately I cannot find where it attaches to so it is just hanging there. Does anybody know where it is suppose to attach and what might happen if I don't attach it.

Thanks...

That connects to the fuel system pressure regulator.
Allows fuel into the crankcase if the diaphram ruptures.

Great Thanks. Where exactly is the fuel pressure regulator located on my 103.983 ?

Thanks again!

It's the gold metal cylinder just under the air filter bolted to the front of the fuel distributor. That vacuum line plugs into the left end.