Intake Vacuum leak?

[VYMAD]

Hi guys, I cleaned my plenum chamber a couple of weeks ago and all has been fine. However just now I was giving the VY V6 the quick once over before a long drive tomorrow and gave the engine a quick rev from under the bonnet. As I give the cable a quick pull there is a half second long sound of intake air as the engine sucks in the quick burst of air and revs go up.
The "air" sound is coming from throttle body or maybe inside plenum chamber, I removed the top of plenum, double checked and re-oiled the seal and put it back together, seems fine. Am I being paranoid, is there supposed to be a momentary vacuum, air sucking type noise as air is quickly drawn into the chamber on the initial quick rev?
Have checked all associated hoses and throttle body bolts too.

[one_and_only2004]

Throttle body gasket?

[VYMAD]

Throttle body gasket?

Was fine when I had it apart to clean and re-assembled, so no, don't think so.
Maybe this is just a normal noise I havn't noticed before. When holding at high revs there is no air sound, just on the point of initial quick rev.

[one_and_only2004]

There is a in-rush noise when you do play with the throttle, mine used to do it too, so yeah I'd say you've just never noticed it before.