Disconnect accelerator cables.
Remove rubber mounts.
Loosen hose clamps (3 and 4).
Remove suction hose.
Unfasten nuts (1) from all 6 throttle valve spigots.
Loosen hose clamps.
Remove idle hose (5), vent host (6) and oil return hose (7).
Unfasten nuts (8 and 9) from oil separator.
Remove air manifold.
Take care of vacuum hoses.
Remove idle speed control valve and close aperture (2). Disconnect hoses (3 and 4) or remove and seal apertures.
Remove vacuum hose (1) from fuel pressure regulator and connect up to BMW Service Test unit.
Measure vacuum with multimeter program (M21). Nominal value approx. 500 mbar. If the measured value greatlu exceeds this, or if it falls very rapidly when the pump is switched off, remove idle strip and fit new non return valves (5).