Got a old mk1 avensis 1.6 with lean burn engine 4a-fe. Looking for info on how the engine operates with regards to the butterfly valves on the air intake from a swirl control valve and vacuum switching valve. Have a haynes manual and no info on this is to be found. The problem i have is the swirl control valve linkage broke a few years ago which i managed to repair. And on its next MOT engine emission jumped up (to much fuel hc?). Have now noticed there is any adjustment screw on the swirl contr