I searched a bit, duke and rc has the same airbox part numbers in ktm partfinder, this behaviour is present on sister bike Dominar 400 aswell which has a compeletly different airboxDon’t confuse the Duke gen 2 with the Duke gen 1 or RC. Different air boxes, different implications and resolutions. Confuse them and you will create a mess that is difficult to resolve.
I'm between doing or not doing things, Hornet 750 will enter my market in 1 or 2 months so i might upgrade to that but if i don't i will probably go all in with the tuning and engine upgrades because this bike is FUNGood point.
but it is kinda funny how they all display the same sinusoidal-wonk, isn't it.
And Noeserd definitely is riding a D390 he's thinking about moderate tweaks to, isn't he.