Mazda b2200 carburetor.

1990 hey guys I'm new to the family of the Mazda truck I've got a b2200 lots of miles I love it. Anyway I idle at about 600 rpms. It doesn't do so great on cold starts and black soot is coming from the exhaust. The engine also sputters at low idling and low speeds Everything else on the truck is fine, for the most part.
I was told to adjust the carbs mixture and idle screws does anyone know a link to a good diagram of the carb?

every B ive had has issues with breathing.blocked up intake or exhaust can also limit your rpms. black soot could be a clogged cat, if its clogged and creating back pressure too much exhaust could recirculate and fuss up your whole intake and egr...ive just had to trouble shoot this same issue , tho for me the weather hadnt been cold enough to constitute a cold weather start....... im just a tinkerer not a mechanic....but the haynes or chilton manuals have been essential references for my tinkering

The stock Hitachi carb is an abortion from the get-go.Runs way too rich=poor fuel economy. Soots up 02 sensor and cat.The reed valves on the air cleaner also get sooted up.EGR valve also has issues. Would be better off going to a Weber or doing a Ford 5400 carb swap.bj