Went for a long drive last night to coventry to pick up a astra gsi front bumper and spoiler After about 100miles on the motorways doing about 80-90 constantly I heard the engine suddenly start tapping very loudly, was quite loud and it wasnt the tappets or oil, the oil light wasnt on or anything. (its a 1.6 8V MPI by the way). I needed some petrol anyway so I stopped at the services to have a look, when i took the fuel cap off to fill up a lot of pressure was released, could hear it release as i removed the petrol cap. After that it was fine, no noises, very quiet again. So im thinking the tank breather must be blocked? and that ticking tapping noise was the injectors maybe? under too much pressure? If it is a breather blocked where are they on a mk3 astra?