Anybody tell me what this is and what it does

[wbski007]

This is off my 92 300CE with a 3.0 you know the one not getting gas to the injectors, I sucked on the vacuum line and it doesn't seem to have any resistance, I still haven't checked the fuel pressure yet, I'm waiting for a gauge, but I thought I'd take this off and see if I could see a filter or screen but no go. Another thing I was thinking of trying is blocking off the return line and see if would run that way??