Exhaust manifold stud removal oddity

[henry caines]

I have a mx5200hst my question is I removed a exhaust manifold stud out the side of the cylinder head and I heard a puff of air come out what does this mean i know its not normal

 

[North Idaho Wolfman]

It happens, pressure was higher when assembled, then when you removed it.
Some will have water / coolant come out when you remove them, still quite normal.