The fuel tank vent is pretty easy to deal with, I've been around the bend on this one before too (including one 50 mile drive at 45mph).
Under the car just aft under the driver's seat (IIRC, might be farther back) you'll find a plastic trumpet thing pointing down. It'll be clamped to a hard line, remove that and backflush with compressed air. If its really buggered run some water through. I'm always hesitant to use solvent on plastic... Easy peasy. I now do this every other oil change as a regular preventative.

In theory there might be a clog farther along the line and it might be worth blowing the line but I'm nervous about shooting whatever the clog is back into the tank...

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Sadly Benz-less