I will also go for h pipe:thumbup.. though x pipe would be more suitable for racing requirements..
..'balance tube' is a common term for h pipe. Basically, it equalizes the pressures between both banks of the engine giving a broader and flatter torque curve throughout the rpm range. It helps eliminate 'back-rap' common on deceleration, and creates a deeper mellower tone both inside and outside of the vehicle.
Hope this bit of info helped you.