I am in the process of replacing my 1997's stock exhaust with a custom 3" stainless steel system. I will be using a Magnaflow polished SS 6" round 3" inlet and outlet muffler and a single new cat to replace the two factory cats. I have researched Magnaflows web site and I am still unclear what cat I need. I know it will be a 3" in and out. I see they offer OBD II CARB cats, OBD II, and just universal cats with no mention to either OBD II or CARB. I don't feel I need to spend the added money for the CARB cat but, is there a difference between a OBD II cat and just a universal cat?