Good mechanics will recommend not using aftermarket cats. It almost always messes up the O2 sensors.So I have used Cataclean and it didn’t work. I’ve used it three times in the past. I changed the catalytic converters and my O2 sensors myself about three years ago. I do smell a strong exhaust smell when the car idles. I’m keeping the car as I’ve put way too much money in it. I had the tranny rebuilt a year and a half ago. And that was $5600! Overall it has been a good car. It is mostly highway miles because my wife used to work in Norman and drove there and back 5 days a week. Now she works from home. As for the comment about the coolant being too low. It is actually over what it’s supposed to have in the reservoir. It is over the hot fill line and the cold fill line. I will try the most easy things first to see if it fixes it. Thankfully it don’t get drove hardly ever. But I still want it to work good.