Are there any check engine lights of any kind on? Jeep to me says TPS. This, alolng with other sensors, controls your air/fuel mixture. Black smoke usually means it has improper mixture. This could cause your Cat to plug but not the other way around. If your cat is bad, you need to replace it as drilling it out will cause problems. Your emissions control system relys on signals sent from your O2 sensor and if your cat isn't doing it's job, your ECM will try to compensate by adjusting your air/fuel mixture, therefore causing more problems. If you have a light on, get your codes read and it will help to figure out what's wrong. Probably a sensor issue.
