Drastic measures. If you are ready to buy a new one. You can give your old one a chance. Cut the darn thing open at the front where the edge of the housing is beveled in around and there is a notch there somewhere. Then pull the thing open, clean it and put a bit of WD40. Put it back together and drill a small hole to put a locking screw on the housing, then use tape to seal it. I have one that it would rev up the engine and would take awhile to rev down. The valve was sticky and cleaning the outside did not help. Now works like new.
More: Make a fuel pressure test also. If you have a crazy idle up and down, it may be the fuel pump or fuel pressure regulator on its last leg.