The egg smell means that the converter is working. My car does it and my friends 02 Honda Civic does it. If I rev the engine alot it seems to go away. The converter will start to rattle when it is going bad. Also I had the same MPG problem as you so I changed my plugs and wire (Boush Platnium +2) and I get between 20-22 MPG with a pretty hard driving. I have a V6