What woulI have an infiniti I30 whose catalytic converter is bad?d you like to ask?

There is nothing wrong with using a universal converter. Your mechanic can weld it into place. If you live in California and have to take the California emissions test you will not p it with a universal converter. If you can save yourself money go ahead. The only difference with a universal converter is that it has to be adapted to fit and it is a little less constrictive.