
Hmm, the video makes me think. The data I would be looking for is not shown. There are a bunch of RED flags in that video. NO ONE drills into a brand new Titanium header and samples only ONE cylinder. The data read from that one cylinder would be irrelevant. You MUST ALWAYS locate a single wide band sensor at the final collector. ANYBODY with simple knowledge knows that.
Dyno charts do not show Lambda or AFR. Or, did I just miss that?
I would have disabled the (2) downflow NB O2 sensors in the ECU (OR used dongles) and then used (2) WB with 18mm adaptors to get a way more accurate reading.
ALL stock GEN II XR's do not make 158RWHP (NET) . GEN 1 is 158 at the crank, GEN II is 162.5HP at the crank. (GROSS HP)
Peak HP did not change at all? Midrange was completely expected with that header design. Are the primaries on the header too large? Is it ECU torque management?
This is why I just don't believe what you see.
Look at the location of the OEM WB O2 sensors on the Akrapovic. They are no where near the OEM location. If you are racing, who cares. You wont use them anyway. When you move the sensors, you really need to adjust sampling timing. Otherwise, you may be adjusting in fuel cells that are later in time (delayed) than expected. If I had to guess, the ECU cannot adjust for this. Autotune systems have settings and calibration for this so you don't adjust the wrong cells.
Further looking at the Akropovic, it looks EXACTLY like the RR header. You will notice that the primary tubes are quite a bit longer than OEM. This is the torque increase. If you are racing, this is what you want when you increase primary tube diameter (top end). Again, racing...not street riding that 99% of us do. This is why i did NOT buy the Akropovic. I'm not at 11500 RPM on the street very much let alone 14000 RPM like the RR. This is where this header design shines.
Look at the Arrow header. Primaries look close to the OEM. All sensors appear to be near or the same location as OEM. Substantially cheaper yet the quality is on par or better. I have used Arrow on 3 other bikes. What I'm trying to say is there is always compromise. Give and take. You really do NOT want a large diameter primary on the street. You lose bottom end and then have to
fuel the sh!t out of it to make up for the loss. When you buy an aftermarket pipe with a similar design to the OEM, you will
absolutely need less fuel adjustment. It makes perfect sense to me as to why you sometimes see a loss with an Akropovic on a GEN I without fuel adjustments.

I do believe the GEN II's will adjust per the defined Lambda table within the ECU.
My Arrow is finally on the way. So, I will know real soon.....