THE MAP SENSOR WORKS ON VACCUM. AT HIGH BOOST THE PRESSURE GOES POSITIVE IN THE MANIFOLD AND THE SENSOR TELLS THE ECU SOMETHING IS WRONG AND THE ECU GOES INTO A DEFAULT MODE OR MALFUNCTIONS.
THE MISSING LINK IS A SERIES OF CHECK VALVES (ENCLOSED WITHIN A UNIT) WHICH IS PLACED BETWEEN THE MANIFOLD AND MAP SENSOR.THIS ENSURES THE MAP SENSOR NEVER SEES A POSITIVE PRESSURE.
WE HAD THIS SAME PROBLEM WHEN MY FRIEND TURBO HIS 1600 SUZUKI BALENO.THE THREE FISH TANK CHECK VALVES WE USED COST $15.00 A PIECE AND WAS NICELY CONCEALED. NEEDLESS TO SAY THE CAR NOW FUNCTIONS PERFECTLY.
THE POWER OF ONE !