"54" gives some good advice above. I'll just add a little to it. Just splitting the pipes from the muffler back won't do anything for the sound or the performance, but will look like duals from the rear. The sound we 6 cyl. lovers enjoy comes from the split manifold up front, 3 cylinders into each side. It gives a much deeper sound even with stock style mufflers and does help the engine breathe easier. I know quite a few "bolters" who only do this one modification to otherwise stock cars or trucks and are perfectly happy with that. But, as 54 says, be aware that one good upgrade can lead to another, and another, and .......well, you get the picture.
