97 mxz 670, where the fuel line goes on the carb there is a white plastic piece inside. is this a filter of some kind. if so, i think i read on here before that these should be removed. am i right. my idle has been kinda rough lately but carbs are clean and synced. it will go up to around 2000 rpm then slowly drop to around 1600 then slowly go back up. any ideas if this isnt the problem?