So my 1997 Jag xj6 is dying at stop lights is my mechanic plugged his computer into it it says the catalytic converters Banks one and two are bad. Would this cause the car to stall like it is doing and if so how much would it cost me to repair it?

 

By the year I think you have an X300 XJ6. This forum is for 68-92 models.
If you re post your question in the X300 forum members with the same model will be able to answer your questions better.

https://www.jaguarforums.com/forum/xj-xj6-xjr6-x300-26/