Nay it's not a sunrrof thing, defo connected to engine. I actually have a recording of the sound but don't know where to post it.... I have a vid posted now, I don't have much gurgling on it... didn't warm up the car properly.
The sound is quite unusual...you have to hear it to believe it.
Can email the .wav to those who are more interested, but here is the vid:

http://video.yahoo.com/video/play?vi...d697bb.1569316