engine Air noise and rough idle

[Wallypug205 1 1 Cars]

Hi all seems like I’m always on here asking questions and getting great responses. So I got the pug started but the idle was rough it went upto 2k then down to 15 before settling at 1k revs however I noticed that there was a hissing noise coming from the engine like air was escaping. I removed the coolant lid and it was bubbling out suggesting air but when accelerated the hissing noise stopped, but was loud around the afm and cone filter area. Has anyone else suffered the same problem?& what is the cure? The leads n spark plugs have been changed and oil. It hasn’t been driven since 2012 since last mot