With Induction kit's it's said not to use oiled but mines oiled and I've not had a problem in 9 years but it is a K&N apollo so maybe the better quality ones are better to use say over a cheaper pipercross equivalent, the Oem is induction is good though so unless you want some more noise it isn't needed. I think the HKS dump valves are the best ones if you wanting the vent to atmosphere on the market but not cheap and have to be careful of fakes we have a guide on here about how to spot one
I did have a bailey dump valve on mine though which was cheaper and sounded good.I've gone back to oem dump valve now. But depends what you want can get forged ones that allow you to alter how it works.