1993 Cadillac DeVille Question: i have a 93 sedan deville and its running really rough and barely running at all

it dont wana go over 10mph like its got bad gas but i put fuel cleaner in it and its stil doing the same thing has anyone else had this problem. i push the gas pedal and its acting like 2 much fuel or not enough and like theres no back pressure but cat conv just got replaced a yr ago