it could be the adjuster / timing chain, cam timing out? ie cambelt not fitted correctly, also check the oil pressure as low pressure can cause the adjuster to fail i hear.
your camshaft sensor is on the left handside of the engine as you look at it,take timing cover off and to the right of the big exhaust pulley theres a little alloy cap held on with 2 10mm bolts, sensors under there.
im sure the ecu will adjust timing n stuff but dont quote me on that .