I removed my bed a couple of weeks ago to change the fuel pump and clearly when I was putting it back on this got trapped under the bed somehow. I haven't noticed any differences in the way the truck is driving, but I'm assuming this doesn't belong smashed under the bed. Thanks!

 

Most likely it's the axle vent tube and yeah you don't want it pinched off like that. It should be as high as possible but open.
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That is the axle vent tube, needs to be clipped back on to the bed.

 

That's exactly what it was. Thank you both for your help.