The yellow relay is on the left hand side facing the engine.. There should be a cover over a number of electrical components (Back of cover says what is there). The yellow relays cover can be pried off....be careful.... Look at the PCB and in particular the main prongs which seat in the connector.. as the prongs go through the board look at the top side where the solder covers the pin .. if you see a faint dark circle the solder has developed a very small crack and when it heats up can expand enough to trip the relay. This is a non-standard relay..ie a printed ckt board with internals which activate very fast and have very close tolerances...it is there to protect the engine from over-boost and provides the "momentary" cut-off of the fuel pumps.
Sometimes if you flick the relay body with your finger it will make contact and work... The first stall I had I did this trick to all the relays... front and back.... and the car started.
John Walker who is a shop owner and contributor to this board was the source who advised me when I first purchased the vehicle and had the stalling problems....
Re-solder the prongs..but be careful about the heat you use...you don't want to fry anything else on the board.
BTW if you don't have the yellow relay ...there may be another standard relay-- Red or Black round one. Try substitution...
Also you may find the car starting right up after it has sit for a while..
1987 930 -Guards Red
2001 740I sport Blk
2011 F-150 supercrew Blk
2014 X3 2.8 white
"What goes around comes around..."