I know that longtubes do add a good deal of power. How much of a gain could you see with longtubes and the stock catback, for noise purposes? Would it be worth the gain/ noise level or would it be a waste of time?
Sorry but I am not too familiar with the catback on the GTO's...
the stock catback on the 05 gtos are considerably good, i plan on keeping the stock catback and replacing with LTs and hi flow cats. You should see a 20-25rwhp gain for LTs and Cats, with the Stock catback. Ive heard people switching to other catbacks and only gaining 5-7rwhp over stock.