catalytic converters

If the cats were bad and plugged, you would see some performance issues. You might instead have an issue with the O2 sensors. Your vehicle's O2 sensors have a heater wire that can go bad making the sensors read an error especially when the engine is not warmed up. You might have also had an exhaust leak (or two) that went away when everything was running hot. The downside to a bad O2 sensor or exhaust leak is that it can cause the engine computer to run rich (by giving it a false lean condition reading), which can cause damage to the cats. Of course the only real way of knowing for certain is to start running a bunch of tests but that can get costly. In the meantime stick to a good brand of gas.

Thanks KenF. Interesting that about 1/3 of the way back home from vacation the light came back on. (it was about 84 degrees outside instead of 101). It does 'sound' like I have an exhaust leak, especially upon first start, so I'll have that checked next oil change. Maybe fixing the leak would essentially solve the problem since it would put the )2 sensor measurement back in line?

Definitely, not only can exhaust leaks throw off computer (and set codes) affecting performance and fuel mileage, but it can also prevent sensor from getting up to temp.