In a stock 05 gto tune, it has the cylinder volume as 0.70819. Times 8..that's 5.66 liters, when the engine is a 6.0. Why does gm do that? I know that effects air mass, which effects other aspects of the tune. In my tune the volume is .73999..so times 8 is 5.91 liters. It was already like that when I bought it, and I've left it that way. If I changed it back to stock, would I have to retune it, and would it even be worth doing?