surging 3sge ( st206 curren)

[eskimo]

Hey,

Quik question. My curren has developed a slight surge every now and then at lower rpm just really sublte, its not getting any worse but im not sure what could be causeing it.

I was thinking a slight vacume leak sumwhere as i can here a very soft hissing?

any idea's to what could be causeing this? Cheers