[Airjer_]

The vent solenoid allows the system to "vent". The purge solenoid is what "purges" or allows the vapors to be sucked from the canister and burned in the engine. Its located between the coils and the firewall right above the O2 sensor. Unless its a newer engine than its right next to the egr valve.

Clear the codes and see if they come back and then worry about them. The cat inefficiency could have been a fluke but if it comes back it should be dealt with! Air pollution is a huge problem, and emission standards are in place to help control them. Many parts of the country require emissions testing but many more are on the honor system. If we continue to stay on top of emissions repairs than likely we will be able to stay with the honor system. If not it is very likely we will all end up with very strict emissions requirements much like California, I really don't want to deal with that.