1990 Civic SI CEL code 9?

Lately I have been getting a CEL code 9, No 1 Cylinder Position code. It happens in the morning, before I go to work. It goes on when I put my car into gear and go about 3 feet. If I warm the car up for 5 minutes, it does not go on. I have changed the distributor 3 times, with a used one and a brand new one. Same problem. I checked the wiring, via the Honda manual and the distributor is good and the wiring at the ECU is in the acceptable range using my multimeter. I took it into a repair shop and they checked for vacuum leaks and timing, and they said it was good and recommended that I replace the ECU. I swapped in an ECU from another working Civic SI and it is doing the same exact thing. The car drives fine while the check engine light is on, but it scares me to commute 40 miles to work. It does not go off in the afternoon when the weather is warm. I did notice that my car is rattling a lot, which kind of started around the same time as my issue. Yesterday I changed the oil and while I was under the car I knocked on the catalytic converter. It rattled a lot, and I see that this is what is causing my rattling. I banged on it a lot just to see if it was internal or the heat shield. I believe it is internal. Today when I started the car, the check engine light came on immediately and even after warming up the car and driving it down the block, the CEL would not turn off. The Code 9 was still the only code blinking. Could my catalytic converter be causing my problem?

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