I bought some headers and now I am looking at a High Flow Cat for my 95 Civic EX. What I don't understand is if I need an O2 sensor in my cat or not. I wouldn't think I need one if one is in my headers but there is one in the hi flow cat i wanna buy.

Do I need the port and O2 sensor in it or get a cat with no o2 sensor port in it?

any help would be appreciated thanks