Always make sure the flexible hose is in place and in good shape from the distributor body to the air ducting on the engine. The twin distributor uses a small timing belt inside. Between the static electricity jumping the gap between the rotor and the distributor cap, there is enough ozone generated to destroy the timing belt. (Ozone attacks rubber, like cracks in old tires) The hose is there to draw air through the distributor to prevent this problem. Incidentally, the 964 has a second hose to ventilate the center section of the tail lights so moisture does not build up.

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