Exhaust Pipe Genius Required.

[stumpeater]

Is there any body in "Cobra Land" who knows the benefit or otherwise of joining the 2 exhaust pipes with an "X" or an "H" pipe on an under body system? I looked on Wikipedia and it tells me there is a benefit in reducing back pressure but which is preferable? Logic tells me an "H " pipe would create a venturi effect as the gases passed the bar of the H, whereas I would imagine the gases getting turbulent as they collided in an "X" join. Any theories, (or links to authoritative web sites) would be appreciated. Thanks Peter.