Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
while your there, you sure theres not leaks? lol
From memory Not and Abba Fan said high flow cats on a V6 is a waste as the stock ones flow enough...unfortunately this was after I bought mine lol. Anyways if you wanna fit the exhaust yourself just go with whatever he recommends. That's what I'd be doing. Send him a PM.