You can get an idea of what the filter looks like by taking a look at the prefilter. It should be kinda clear/opaque which lets you see if the filter element is clean or black. I'd change them anyways.
You can check the venting of the fuel tank, by pulling over and opening the fuel cap. If you hear the sound of air rushing in, the tank had created a vacuum and you have a vent problem (plugged/pinched line??).
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.