im not sure why, but on my mk3 the oil pressure light will stay flashing when i run the engine with the alternator unplugged or the belt is off. when i tried to figure out why it was flashing, i checked the two sensors, and the head was showing no oil pressure, plug in alternator, head shows oil pressure, light goes out. So id say check your alternator connections, and make sure its not a bad alternator.
wow, NOTHING at the head? is the head gasket installed correctly?