2nd catalytic converter
 

Didn't want to get the new car thread to OT. I thought about doing this but could not find any data that it would help. By adding a 2nd cat would it really reduce emissions? If the first one not doing the job why would the second one? It would take it much longer to get to temp because it would have to be futher down thus reducing it's efficiency by prolonging the time to light off.

Many cars have a second cat (or in the case of my Mark VIII a third, one on each bank and a y pipe with one) to reduce emissions st startup. It takes a while for the first two to get hot and get going. This one is msotly for cold start emissions.

Yup, depending... Like you said, if unburnt HC emissions from the first one are low enough, the second will have trouble or never light off. In fact, I think that's why my Camry runs so damn rich on start up. I used to fill up the tank, go two miles down the road and through a drive through, go back to the station to fill up, and found out I get ~8mpg during really short/cold trips. Unless the ECU is programmed to light it off, or the current cat is nearly dead, I don't think it'd do much.