Hi.
From memory (don't forget it was a long time ago 1995) what was happening was that the injectors were drawing slightly too much current causing a bigger inductive kick spiking the ECU which would falter and struggle to control the idle control valve. It would only happen once in a blue moon.
The only reason I remember is because it nearly drove me over the edge.
I wondered for years how BMW figured it out (the fix was a TSB I did not find the problem).
The power of a scope and somebody who knew how to use it.
I'm glad you got it sorted.
Fiachra.