Smoking from cat converter

I was on my way to cape cod this friday going about 90/95 for about a half an hour and it started smoking, its only got idiot lights so i had no idea as to the engine temp or oil pressure but i got over to the side and found out it was coming out of the cat converter. I kept going but at the legal speed limit and it went away and it was fine all weekend around town. Is it just time for a new cat or is there a bigger issue, its a 96 4 litre with 165,000

If you take it to aReputable muffler shop or one you trust they should be able to tell if it's plugged Should be no charge...