I woke up to a quiet car, and I don't like it.
 

Hello all, so here's the deal. There's a car meet tonight so I spent yesterday preping my car. I start my car and leave for work today. At the Dunkin drive through I put my window down and boom, car sounds no different than a Prius. Floor it down the street and I have NO power (but now that I can actually hear my air intake it sounds sick). So here's the thing: has anyone ever heard of you cat getting all gunked up OVERNIGHT? We're talking the exhaust going from ear bleeding loud to pathetic attempt at sounding race car in about 10 hours. Also I'm done work at 7 and we have to leave by 8, any quick fix to make sure this is a cat problem? If you think this could be anything else please let me know. 1985 Z31 N/A, cat-back straight pipe, cone air intake, was a vacuum leak but shouldn't be related.

Thanks in advance.

Cold start vs warm engine
 

When you first started your car and got out of it perhaps it sounded like a race car because it was a cold start. Engines are always louder when there idling cold. Then when your in the like there’s a lot of stoping and starting which does a great job of heating up cars then that’s why your exhaust sounded quite again. Give your car time to cool and try starting it again.just my best guess.

Clogged catalytic converter(s)
 

Sometimes a car will get a clogged cat where the honeycomb fiberglass that quite your car heats up to much and comes apart causing your exhaust to be loud for a short period and then clog from the loose fiberglass.

Testing
 

Some times if your cat is clogged bad enough if u start your car and put something in line with but not blocking the exhaust Tip small shards of fiberglass will hit the item.