What it the stock ls exhaust size? This header has a 2 inch outlet, will i find any gains if i put it on with a full exhaust system? I want to go turbo but first want to do my exhaust. Thought i would go with a 2 1/2 or 2 3/4 inch setup. I don't want to buy another exhaust header because i will replace it with the turbo exhaust manifold.