1994 honda passport shakes o the passenger side whil driving at normal speeds?
 

i was told that the vehicle needs a catalytic converter and exhaust system, but it rides like the tire on the passenger side is hitting small bumps in the road when it's not the tire pressure is fine whats vccausing this secondly it makes a rattling noise which seems to be coming from the rear somewhere what could be causing this and what does a catalytic converter do...finally where is it located on the vehicle

you might have a bad tire take it to a tire shop and have them check it out for you and the catalytic converter burn all unused fuel from the exhaust. the ratteling might be a broken exhaust clamp or heat shield. now if your ses light is not on then you dont need a catalytic converter so dont pay hundreds for one.