rogers,

A car in good tune should not have exhaust odor. As George says, either oil or gas in the exhaust. If you can smell it, it is not in good tune.

Go to a shop that has a five gas analyzer. Once you know the gas mixture coming from the pipe you can address the source. Here is a pretty good short primer on exhaust gases:
http://www.autoshop101.com/forms/h56.pdf

You can install a Wide Band Oxygen Sensor and reader to tune for maximum efficiency. This is probably the most cost effective change you can do to maximize tuning without major alterations to the car.

You can retrofit fuel injection. Make it MegaSquirt and you can tune to your hearts content.

You can add a catalytic convertor. You probably shouldn't do this until you change to fuel injection. A continuous rich mixture will overheat and destroy a catalytic convertor. You need a closed loop system to control the mixture before you graduate to a catalytic convertor.

You can drive the car less often. (Seriously, if you cut your drive time in half, you lower emissions from that car by 50%.) This is probably the least satisfying but most effective method to reduce automotive emissions.

--
Mr. Shannon DeWolfe -- (I've taken to using Mr. because my name tends to mislead folks on the WWW. I am a 52 year old fat man ;-) -- KD5QBL