whistling sound under acceleration

[BananaClip]

I've noticed recently that at full throttle at 4-5k rpm my 944 has a bit of a slight whistling noise. Can't tell where it's coming from, and it's not really loud, but its just noticeable and it has started to bug me a little. I never really noticed it before a few days ago. The vacuum line to the fuel pressure regulator/ damper is disconnected at the check valve. Could this do it?

[fast924S]

Well, First things first you should have all your vacuum lines connected, With out it on your screwing up the A/F ratio, Other then that u need to find where its comming from, Is it the enigne? is it bad weather stripping?? ect..