I think that the approach to power up by increasing the inhalation efficiency is a custom that is easy to realize.
There are various products, but the most popular item on this site is the KSPP high-efficiency large-diameter intake funnel! It has received a great response since its release.
The good thing about this funnel is that you don't need to process the exterior covers.
In addition, the product comes with a pattern paper or a guide necessary for enlarging the hole in the genuine air cleaner box, so there is no mistake in drilling. If you put this intake funnel and an external air cleaner, the intake efficiency will be improved. It is more effective to remove the genuine snorkel and use it as an intake cover.
If you are looking for an absolute flow rate, the metal one introduced on this site seems to be more expensive, but if the displacement is normal, this one is more compatible.
If you introduce a large diameter throttle body as the next step, it will go even higher...
