Why is My Webber Cardb Stick'n!

I put a Webber Carb on about 3 months ago, and this past week it feels like it wants to take off after i take my foot off the pedal. I notice that there's noo spring on the back side .Why is the throdle stick'n? Plus the little rubber plugs you use to plug up vaccume hole's keep pop'n off and i gotta replace them all the time.Thanks for looking and your answer's!!!!!

the plugs can be glued, threaded and capped, or something...and put a spring there?