I went to Austin to visit my cousin and he has a '00 Lightning with 4 pound lower pulley, CAI, chip, and catback. Normally I would pull him hard in first and second and then kind of inch away in third. I had to put on my cat for inspection and we ran again. This time he pulled on me!! I could feel the restriction with that cat but I didn't realize that it was that much!

 

Are you sure he didn't do anything additional to his truck? When I had a pair of cats welded on, I didn't notice any change in performance.

 

Yea I agree, no performance loss was felt. My idle quieted down but that was it.

 

HF Cats should not cause a huge restriction, unless they are clogged.
I bought a set of R/T cats years back that were like that. They were
promptly disposed of and replaced with something better.

 

There was nothing different to his truck and the only difference is that I had the high flow in place. I also notice that I had about a 2 MPG decrease in my fuel economy. I know the cat isn't clogged because I hardly use it except for inspection time and it visually looks to be good as well.

 

. . . indicating something else is wrong with your car. Cat's should not noticably affect gas mileage.

 

There isn't anything wrong with my car. It happened ONCE I put the cat on.