For starters, here's the relevant part of Texas penal code which GP mentioned. You can read the whole thing, it's very short:
https://texas.public.law/statutes/tex._penal_code_section_9....
IANAL, but it seems you can shoot someone in Texas for stealing your catalytic convertor if you "reasonably believe the deadly force is immediately necessary" and the catalytic convertor "cannot be protected or recovered by any other means."