What Does This Hose Do?

[Jezimp]

Hey guys. Im new to this sote so i appolagise if my termanoligy isnt up to scratch.I brought a 93' r33 not long ago. It has an after market bov, and I'm goin thru the process of fixing the problem of the car stalling and idleing s@*t house. I cleaned the idle control valve and noticed there is a tiny little fitting ( I'm presuming where a hose is meant to be clamped onto) right above the control valve but I'd had a crappy little rubber cap zip tied onto it which was was r**ted so I took it off. Havnt stared the car yet incase it is something major. Just wondering of you can tell me what it does, and if I can just cap it again for now until I out the original blow off recirculator back on??

Any help would be greatly appreciated

Thanks