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.

Porsche 928 Alignment Tips
Porsche 993 Alignment Tips
Boxster Bike Rack Installation
Rebuilding the 914 Rear Brake Caliper
Proper Clutch Cable Installation
Porsche 914 Clutch Replacement
Clutch Tube Repair Procedure
2.0 Liter Engine Rebuilding Guide
Fuel Injection Operation
WEVO GateShift Installation Instructions
Engine Oil Galley Plug Replacement
Engine Removal
Push Rod Tube Seal Replacement