What is it? There's a hole in the end, but it either doesn't go all the way through, or mine is clogged with something rock hard.

 

Any pics? Not sure we understand. You talking internal or external? If internal, I think you may be talking about the overflow tube. When the bowel is full and the needle float valve stops the gas from entering, any excess goes there to dissipate or be vapor scavenged in an external hose with a screw capping it off, on stock 50 anyways.

Like I said, pic would be helpful.