looks like the manifold has cracked, i tried to sort a mysterious blow coming from the area the other week with fitting some washers as it has a habbit of being blowy on start up and quietens down when warm. i noticed a tiny crack between pots 3&4 so gave it a wipe over with some gun gum. sure enough its back again now and my fears are that its gone on the underside of the manifold.
looked at a dbilas one as they are stronger and dont want to be faffing around when babies get here. loos like cs4 will be shelved now. not a happy bunny.