SamkrovR8

The car first off is a 2005 Sports Edition Automatic with 4 Gears. I just hit 64k miles on it and replaced all 4 spark plugs and ignition coils at 60k. The car has a error code of the Catalytic Converter, I don't remember the exact code but the guy at Advance told me it was the O2 sensor for the Catalytic that most likely went bad.

I question it is the O2 senor because a month back I decided to take the car out to see what I can top it off at (The Cat error only happened about a week ago and may be unrelated). At 4th gear around 5000 RPMs it took around 3 minutes to climb from 97 MPH to 101 MPH where the car just sat there and and RPM never exceeded 5000.

At first I thought it was a the governor, but it suppose to stop at around 120 MPH. So now I am left with a dilemma which I can't figure out. I have a few thoughts of what is going.

*The Cat may be clogged giving off the error code causing the car not to go past 101 MPH.

*The Cat is fine and it's really the O2 sensor bad but what is causing the car not to go past 101 MPH.