Dyno numbers - 2.5inch Headers vs Stock headers

[sunny]

I have just seen a dyno run with a Paul Bryant header and exhaúst that made a good 40hp gain over stock.
It was an unrestrited map and AFR adjusted. As you usually get about 30hp with just an unrestricted map it is about another 10hp with it.
And the engine was otherwise stock.

so I should see 10hp gain, perfect!!!! I just got the kit, I am welding it

 

[Nashvegas]

Youre gonna be close to 200hp. Torque will be high, you know Konrad will tune where engine is happiest not max numbers, VE will be over 100 throughout just about, there are a few spots that are hard to get over 100 but its gonna be a bad machine! You should have Paul put ports in the top of each tube for tuning, Konrad can dial in each cylinder then like he does on mine. And then with the ports in tubes he can run the knock test when you test drive and make sure timing is happy on each cylinder.

Paul said no problem to add the ports! @Kevin frazier

 

[Gimlet]

what I dont understand is throttle response on the bike with open headers is way better than before, huge difference, I move throttle at any gear and it goes which was not the case before.

Initial throttle response is down to how the ride-by-wire graduated throttle ramp is trimmed. Typically, most bike manufacturers give you nowhere near a 1:1 throttle. If you open the throttle 10% from fully closed you'll typically be getting only 2 or 3% of what you've asked for. The wider you open the throttle the closer you get to the true amount that you've actually dialed in with the twist-grip, till you've got the throttle wide open against the stop, then you get the full 100%.
You can trim a RBW throttle to make it 1:1 (if you've got the software to crack the ECU, of course) but it would be extremely aggressive and snappy to the point where the bike is all but unrideable. This is especially true of high performance big V-twins like Ducatis and KTMs. You'll find many dyno tuners who've been asked by owners to map a 1:1 throttle and they've advised against it but the owner has insisted and a few days later they're back again saying, OK you were right, I can't ride that. Please tone it down a bit.
Many tuners will tell you that the closest you want to go to a 1:1 throttle is 80% of the power you've asked for coming off a closed throttle.
Tuners can change the curve of the throttle ramp so it starts at the manufacturers 2 or 3% but then rises more steeply than stock the further you twist the grip. It doesn't add any power but leaves you feeling that you're no longer waiting for the bike to catch up with your brain when you open up. This will make the bike feel vastly more responsive without making it excessively snappy. But it's a time consuming business because of the number of throttle opening positions they've got to work through to produce a progressive curve.