pulse noise coming out at intake air opening

Complaint is when cold starting there is a noise mimicking a slight exhaust leak that goes away when it warms up only to be replaced with a pulsing noise coming from of the intake air opening, not loud but obviously present and increases frequency as more throttle is applied. there is no trouble codes or check engine light, egr seems to test ok engine stumble etc when vacuum applied. no performance issue that I can see. Was wondering if this was ever a reported issue and if so what solved it. Or is it normal being more diesel tech than gasoline could use some technical advise from someone in the ford industry.