I ran 10.5 -1 rc 315, unported head with a good valve job and springs, Webers.
The Webers gave far better response.. Better low end.
The head i suspect worked better low down , but suffered on top end..a tradeoff.
When I raced it the first year, and then later on (not the whole time) i ran the turbo header..smaller primaries.. Done on turbos for a reason.
However, believe as a side effect, it increased torque.... Again at the expense of maybe topend power.
Although the turbo header is unequal length, it still worked well, and allowed me to drastically lower the bike.
That did certainly not hurt launching the bike. The motor had started feeling less power and running slower..but lowering it helped..got 2 tenths in the 1/4 mile gain. That surprised me.
Then I started noticing that if I rolled it on a quite low RPM, it still pulled hard..
So there it is.. I was pretty happy with it and decided not chasing ET...that having the torque was more fun and more useable..
And I really have no one elses experience to compare to.. Only ever saw one other bike with a pipe like that, at Sturgis..never got to meet the rider..
But this year, I should get dyno time.m