car trouble

98 plymouth voyager black smoke coming out of tail pipe when i start it up .also when i drive it wont really excelerate that fast take some time before it revs up to excelerations after sitting for a day or so when i try to drive it starts to put like im running out of gas then after a couple of minutes or so it will then run right someone told me that it might be a catalic converter i dont know but the service engine and air bag lights are on and been on for a while just got a tune up and problem still exists i got a diagnostic test and it stated that i need two sensors got them havent put them on yet