rb25det noise?

[dreamin240sx]

hey guys i have an rb in my s13. the dam thing runs amazing. i have it on 7 pounds and the only upgrades it has is a greddy timing belt, fmic and exhaust. well it makes a whining noise when idling. but when you rev it up it goes away. also it goes away as soon as you pull the oil cap off. My friends and i think its the pcv valve but before i buy one im wanting to get a couple of extra opinions. thanks for any help guys

[dreamin240sx]

any help is appreciated and yes i did search just cant get a straight forward answer

[DJDANGER24]

Just buy the PCV valve, they are like $8 or something like that. And if it's not it, then you have a new PCV valve and repost.