Strange blow-off valve like noise on start up

[MPotyondi]

For the last week or so, every time I do a cold start, I hear what sounds very similar to the noise my blow off valve makes.

Prior to the last week though, I never heard that when cold starting. It's on a 1989 240sx SR20DET.

I don't have the knowledge to go snooping around the engine looking for problems, I wouldn't know what to look for. Should I be concerned about this sudden irregular sound?

Thanks

[HeyKai]

How high is your idle when starting up ?

[sr20s14zenki]

Vacuum leak, what bov do you have, type s by chance?

[MPotyondi]

Idle is around 1. Sometimes slightly higher or lower.

It's an HKS bov that's all I know.
Zenki, how big a problem is a vacuum leak?

[avow]

I would start with the HKS SSQV bov. does it have the purple ring in it?

[MPotyondi]

I didn't see any purple ring, don't know.

What is the normal idle for an sr20det?
If my idle is normal, does it mean I don't have a vacuum leak?

When I was driving tonight, I could hear the sound whenever I accelerated quickly, sounded like letting air out of a tire. At what point is it normal to hear the BOV and when isn't it?

[avow]

are you sure you are not just hearing the turbo spooling? i asked about the purple ring because that is the revised one. if you have one with the black ring they are know to leak if i remember correctly.