mazda b2200

ok, i dont know alot of mazda trucks but my friend has one and everytime you start it it runs for about 15 -30 secs then it idles and the idle is ruff and it dies, i took the air filter off and i noticed that the breather filter is pich black, also the air filter is dirty, could that cause the problem?i am also planning on using carb cleaner to clean the carb

Choke is not properly set, float in carb is not properly set. Cleaning carb with carb cleaner is OK but I would use Seafoam instead. Once carb is clean find a Haynes manual for truck and set carb choke and it should run much better.