How does it idle if you disconnect EDS, or at least the ELR actuator at the tail end of the IP? You might have to help it idle by leaning on the throttle linkage so it can sustain idle. What I'm interested in is whether it idles smoothly without EDS. My guess at this time is a bad ring gear sensor or bad wiring between the ring gear sensor and EDS.

Sixto
87 300D