beginner questions on hi flow cats

[Andy 98RT10]

I started modding my car, and I've decided the next step is high flow cats. I have some beginner questions though, any help would be appreciated:

1. Would they be bolt on, or would cutting / welding be required?

2. Are they 50 or 49-state emissions legal (In case I move and take my Viper with me)?

3. After how many miles, since new, will the stock cats start clogging up and decreasing performance?

[Ray from NJ]

1. Would they be bolt on, or would cutting / welding be required?

-Some cutting and welding will be required.
You have a choice on weather you want to cut your stock cat/flex-pipe assembly or find a donor assembly at one of the tuner shops. They usually have lots of them collecting dust in a corner somewhere.
I don't think it's possible to get a good seal from using only clamps where the reducer meets the sharp bend. Measure it twice, clamp it in place and take it down to your local muffler shop to weld.
Make sure you pressure test it with air or water before installation.
I found some pin holes after installing mine and had to go back to re-weld them. PITA.

2. Are they 50 or 49-state emissions legal (In case I move and take my Viper with me)?

-Most states use OBDII testing on 96 and up. Since they can't see the cats, they rely on the computer. No codes, no problem.

3. After how many miles, since new, will the stock cats start clogging up and decreasing performance?

-As long as you keep up with maintenance and the a/f ratio remains optimum, I think they should last as long as the car.