I have an 88 and had a similar problem, a minor hesitation at low rpm's once in a while got gradually worse until it would stall at least once every day. I changed the ecm, the crank position sensor, the spark plugs, the fuel pump relay, the TPS, the distributo cap and rotor, the plug wires. My friend the BMW mechanic said it couldn't be the coil because he tested it and said it was fine. Well guess what after swapping out all those parts I changed the coil and the problem is gone... spent almost $2000 in parts and the problem was a $50 coil.