haha no worries, I guess I left out a few deets in my post.
Ah right, the boost is a little bit unstable in this region... I may play with the PID tuning as it looks a bit too agressive. But I think you may be right that the runner length exacerbates it. I remember when we made a gsxr gokart back in the day we tuned the intake and exhaust so we had two peaks to spread it out. I guess the exhaust header and intake runners much be tuned for the same frequency in this case.
It feels smoother than what it did for sure, before the tune it was a bit jerky. I actually thought it felt slower after the tune, but actually it was just the smoothness. Was just curious if it should be expected, but it seems like it is and you are right the scaling is quite bad so it makes it look worse than it really is.