Hi Chaps, Still getting a ticking/clicking noise coming from back of engine bay. Took to local garage and car put on 4poster. Mechanic reconed exhaust leak from either manifold gasket or front pipe to manifold gasket. Bought both from my local Vauxhall dealer and booked car in to my local garage for fitting. On my return to pick my car up the mechanic advised they had replaced the front pipe to manifold gasket but on checking the manifold one found it to be intact so didnt replace. Although a bit quieter the ticking/clicking noise is still there. Started the car from cold an hour ago and all was quiet. A few minutes later the tick started. On going over with my trusty stethescope i notice a loud tick from 2 places. One is the pipe coming from the charcoal canister to the PCV and the other being the air feed pipe going into the plenum. I have had a Purge control valve go faulty in another car years ago which was a similar noise to this but unsure. Can anyone advise what feeds the air intake pipe on the rear of the plenum? (of the four pipes going in its the 2nd from right)