Catalytic Converter

How do u know when the Catalytic Converter on a chevy impala is failing whats the symthons?

my 2002 impala had the CAT go bad at 70,000. Usually there's a loss of power. I went to a steep hill in town where I live and got on it pretty good and there was no 'get up and go'. I took the car to lee myles at first thinking it was a tranny problem. They confirmed it was the cat. Took it to the dealer and they replaced it under warranty. I had received a letter from GM 4 months prior stating they raised the warranty to 10yrs 120,000 due to the number of problems.

Also , I've had a clogged fuel filter cause acceleration problems in my '86 cutlass cierra (4cyl) and '90 s-10 blazer (6cyl)

did u have the full warrenty or u had a extendent warrenty?