To be honest you can hear (just very slighty though) air leaking from somewhere but have no idea where its coming from so its very hard to trace i suppose your right and the best thing to do it just take all the intake lines off and check them all.

I also noticed that the air filter (its an original one with the black plastic case) isnt secure. But when you remove it you can see the intake line has like its own butterfly so it wouldnt be leaking air through there then on idle would it if its gonna be closed?

Just thought id mention again that it can be driven no problem and doesnt missfire... its just whenever it comes to idle - 75% of the time it cuts out