1992 940 turbo. Sudden loss of power, engine runs but sputters and shakes. Found a bad plug wire and replaced wires, cap and rotor, tested and cleaned idle control valve. Ran better but still shaking, so checked compression: 120, 105, zero and zero in cylinders 3 and 4. Oil is clear and no smoke from tail pipe. Have not opened it up yet to take a look, but the engine is running much stronger than what two cylinders would produce. Blown head gasket between 3 and 4?