WJ Worn Pump?

[Blueevo]

I have a 1999 Jeep WJ with a 4.7L. I had recently heard a knocking noise coming from the engine compartment. It isnt the motor, but i did narrow it down to a small pump mounted on the driver side fender. It has one tube going into a large black box and another going into the throttle body. I was wondering what the pump is/does and if it should be making a knocking noise.

Thanks for any help!