Code 45 - Rich Exhaust

While driving my 89 Caprice, the service engine light came on. The error code was 45 - Rich Exhaust. Since then, it has come on and off.

Looking online, helped a bit. It initially failed emissions earlier in the summer due to a vacuum leak, but was quickly repaired (enough to pass the test after)

Could this be caused by the vacuum leak? (car smells of gasoline when running). Is the best remedy to just replace the whole exhaust? Does anybody know if I just keep driving, if it'll result in long term damage? thanks!

Could be due to that, a plugged injector, or simply a dirty air filter element. Replace your air filter (CA326) and see if that fixes it.