Renault clio 16v 52 plate Exhaust popping and hissing from engine

My Renault clio 1.2 16v 52 plate has been sounding a little rough for a few weeks now and noticed there is popping coming from the exhaust and also hissing coming from somewhere in the engine... it sounds like its air escaping but im not sure.
The spark plugs have recently been changed.

hope someone can help me find out what is wrong!...thanks in advance.