Fuel sending unit.
I have a 2007 Cobalt, and I have to replace the fuel sending unit do to a crack where the elbow comes out of the fuel fuel sending unit. On top of the elbows there is an "S" and "R" I'm guessing that is SENDING and RECEIVING.
On the fuel filter there is two lines that come out of the filter plus the out line to the engine. The other two, is one for sending and receiving. I forgot to mark them. Thank you!