The oxidation catalyst replaces the trap oxidizer. The cat is along the exhaust pipe beside or behind the transmission. It looks like a catalytic converter. This is a TD exhaust system which is similar except for the transverse muffler. The cat is the first device flowing from the engine -



The shutoff actuator/STOP lever has some effect in cutting fuel when it's anything but fully vertical. Beyond disconnecting the vacuum line, wire it in the vertical position while diagnosing. Note that the key won't shut off the engine while the vacuum hose is off and the lever is wired fully vertical.

Sixto
87 300D