[Raceboy]

Originally Posted by RarlyL8

Street turbos spend little time on boost which is where a properly sized tuned system helps out. There is also a bump in HP at the top end as the organized pulses hit the turbine in order.

This only applies to single-entry turbine. Twin scroll turbines with properly split (1+4 and 2+3 on 4cyl, 1+2+3 and 4+5+6 on 6cyl) exhaust manifold will neglect the necessity for making long tube headers. Thus, with twin-scroll turbine you get the best of worlds: short headers for fast spoolup+compactness without having to sacrifice top end.
Tube sizing is important as I said it already in my last post because the slower exhaust gases flow the more heat they lose -> less energy for turbine.