To remove the camshaft cover, mark the rocker arms 1 to 4, with No 1 nearest the timing belt end, to ensure they are refitted in their original locations; failure to do so requires a basic clearance setting procedure for the injectors. Loosen the locknut of the adjustment screw on the rocker arm above the respective injector and undo the adjustment screw until the rocker arm rests against the injector's plunger pin. Gradually and evenly slacken and remove the rocker shaft retaining bolts, starting from the outside, then lift off the rocker shaft and discard the old bolts, as new ones must be used. Before refitting, check the rocker shaft, rocker arms, and camshaft bearing cap seating surface for wear or damage. Apply grease to the contact face of each rocker arm adjustment screw, then refit the rocker shaft assembly, tightening the new retaining bolts from the inside out, first hand-tightening, then to the Stage one torque setting, and finally to the Stage two angle tightening setting. Attach a Dial Test Indicator gauge to the cylinder head upper surface, positioning the probe against the top of the adjustment screw, and turn the crankshaft until the rocker arm roller is at the highest point of its camshaft lobe, ensuring the adjustment screw is at its lowest. After establishing this position, remove the DTI gauge, screw the adjustment screw in until firm resistance is felt, then turn it anti-clockwise 180° and tighten the locknut to the specified torque, repeating for any other refitted injectors. Finally, reattach the camshaft cover and upper timing belt cover, start the engine, and verify that it runs correctly.