Gargling Noise From Intake

[NyteEscape]

did the timing belt last weekend. after it was all said and finished, i started her up again. then i started to notice a gargling noise coming from the intake. didn't really know what it was. took off the intake to look around, didn't see anything unusual.

the filter is about 500 miles old, so pretty much brand new. it's the stock airbox, so nothing different there.

i recently did a spark plug change, (http://audizine.com/forum/showthread.php?t=229442) and noticed a little oil. i think it may be a valve cover gasket. do you think this may have anything to do with this?

other than that, you have any idea what this could be? starting to get a little paranoid now as to what this could be.

i'll see if i can get a video or sound clip tomorrow.

Edit:
also, the check valve right above the intake is broken, so i'm going to replace that soon. i don't think that's the reason because when i cover it the noise is still there, as in there is no change.

[AudiA4Turbo22]

mine gargles all the time, at idle it'll gargle, more noticeable if u have an aftermarket filter.