I've had the same problem with my 89, B234, 145,000 miles. Every so often, it will run poorly wanting to stall, poor idle, smells like gas, then fix itself. Over the last two years it has had new plugs, wires, cap, rotor, crank sensor, temp. sensor, intake gasket,fuel regulator,injector seals, O2 sensor, idle valve and the fuel pumps have been changed. Swapped AMM and that didn't help either. My next items to investigate are coil, throttle position sensor, radio suppression relay, knock sensor and power stage. I have heard these cars had issues with weak coils, but mine checks ok. I'm thinking some issue in one of the above items may cause the rich/lean condition, even though they are mainly ignition items. I'm open to ideas too. Thanks.