2001 Honda Civic Timing Belt, Tensioner, Catalytic Converte

2001 Honda Civic 92000 miles

Had timing belt replaced. Two weeks later, started on a cross country drive. After about 1000 miles, in hills of West Virginia, engine light came on and car slowed down. Took to a dealer. First said it was the O2 sensor, then said it was out of time. They wanted to replace the timing belt. When told the timing belt was new, they said it was the tensioner. Replaced that. (Took 4 days). 10 miles down the road, same symptoms. Took to another mechanic and he replaced catalytic converter. Car runs fine now. First mechanic now says that being out of time ruined the catalytic converter, so not their problem. But they say that catalytic converter was ok when they had it. Is that possible - did being out of time ruin the catalytic converter after driving 10 miles after the tensioner was replaced? I have a sneaking suspicion that we didn't need the tensioner, that it was the catalytic converter all along - but I don't really know much about cars.