May have solved stalling 930 problem...
 

Previous owner had installed "secret" kill switch for fuel pumps. He ran ground wire to hidden switch burried in temperature control module housing between seats. Craftmanship was pretty dodgey and I expect that sloppy and aged connections intermitentently failed. I removed this lash up and also isolated two pump relay hot wires to separate fuse blocks. Finally rewired ground wires to a more substantial and secure connection. Imagine the problem has now been eliminated. Thanks to all for input and suggestions.

EPS

Congratulations, sound's like you're a little better at wiring problems than some of us (like me :D).