This is why I recently posted my test results and how they came about. As said, seeing all the numbers is important.

To do as the OP was told, or Not have the car warm, would mean taking it to shop in the first minute or two of operation at most. My temp gauge is at normal within 3-4 mins, so getting to station before that, and having test done as one rolls in, is quite unrealistic.

Cat needs to be hot to work, true, so highway or uphill is recommended beforehand. 02 sensor is vital, but mine was a few months old.
Water torture will clean out carboned up cc without other chemicals, although I am intrigued by AutoRX for longer term attempts.
My experience indicates importance of correct fuel pressure throughout range, I think.
As it turns out, after new fuel pump and filter my car passed even with a cracked vacuum line which I didn't find til later accidentally.