big black ball

i'm tryin to clean up under the hood of my s10, just gettin rid of unnecesary parts like washer fluid reserve and such. then i came across this black ball hangin from my hood and it has a little hose ran from it. does any one know what this ball is for and how necesary is it? by the way its a 97 4.3

thanks

that little black ball holds vacume to control your heater duct door to change the settings form defrost, floor, dash, and so on. you can t it into the brake booster i guess since it holes vacume also.