Briggs Intec 20 horse power carb

I have a Briggs Intec 20 horse power vertical shaft engine on a Cub Cadet zero turn. A couple of weeks ago it didn't seem to have enough power and when you turned your head you could hear the engine sort of sputtering. Not missing ... just not running smoothly. Like it was short on fuel. So, I disassembled the carburetor and along side of the brass nozzle that has the little holes in it that dips down into the fuel bowl there was a chaff like substance plugging the area. Cleaned the carb up, bought a couple new gaskets and assembled. Runs better - good power - might be a little rich. HERE IS MY PROBLEM - when I dissassembled the carb a little brass orfice with a tiny little O - ring fell on to the work bench. It is truely a little round piece of brass with a hole in it. Where does it go???? I dropped it down into the white plastic part that the brass nozzle goes into. Didn't know if it went there?? Could it be the seat for the needle??? Or, does the needle valve just seat in the white plastic part??? Has anyone ever worked on this one barrel carb??? Only comes on the Intec engine from what I can see in the Briggs manuals. Not a Briggs carb. - Briggs bought them for this engine. Thank you.

In most cases it goes in the plastic tube thingy that slid up over the brass nozzle.
if there are 4 passages in that tube, there should have been 2 of those orifices. (In most cases at least.)
I tend to blow them out-and away- when I am cleaning a carb with compressed air.

Its the jet and no wonder its a "little" rich. would probably be smoking.

get the model and type number and look it up. should be a breakdown picture of your carb. on the engine breakdown that will show where it goes.