Round-conical breather — TA Technix

The performance filter fits into the original airbox in place of the cartridge. Its mesh lets more air through over the same surface area: the power gain is modest and honestly barely noticeable on its own, but it involves no cost, risk, or tuning.

Its real benefit is economic and ecological: it can be cleaned and re-oiled instead of being thrown away. Over a car's lifetime, it costs less than replacing a cartridge every two years, and it affects neither the sound nor compliance.