On my 2barrel Motorcraft carb I noticed in the front they're are two screws tword the bottom of the carb. Are these both the mixture screws? One for each barrrel maybe? If so, what would they be set on? I may take it appart and clean it an put a kit in it. Anything I need to know or watch for? I've done a one barrel in the past and lots of motorcycle and small eng carbs.