84 b2000 anybody know what this is?

I have a 84 B2000 that I was having problems with studdering at half throttle... Changed the fuel filter and cleaned the carb with no luck but took this off and the truck runs great again.. Anybody have any idea what this is.. It says fcv on one side of it and it was mounted in front of the gas tank the fuel line came from the pump into one side then back out the other.. It rattles like it has a metal ball in it and you can push air through it one way but not the other.. Im thinking its some type of flow control or backflow preventer.. Anyone have any input on this?

I think its the Fuel Check Valve

I'm guessing it's not necessary? It's running fine without it...

Maybe a picture would be better to diagnose it

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://images.tapatalk-cdn.com/15/07/01/a56ff1fa430d935c27f0ab678441d1f1.jpg.
Sorry I couldn't figure out how to post pics...