gas odor

my buddies 95 ls is a PoS car, suprised it can still run, but however my concern is the odor is exhaust is making from outside the car. to my suprise it has a full cat-back exhaust on it, not sure of the brand however (came with the car) but the problem is the engine exhausts emit a bad odor, one of wich the catlyitic converter and/or muffler should. this leaves me to beleive that there is either A no catlytic converter, mind u i haven't been under the car to take a gander, or there is a leak in the exhaust system before the catlytic converter. no i am not sure wether it is a leak, the engine is running right (135k miles and 10 years old), or it is just normaly, the smell is tremendouly strong, it is as if you were sitting right be hind the muffler. whatever, the reason he doesn't post it is because i am the "mechanix" of the group.