Years back, I was hearing a chirping sound after I did a tune up. I thought it was maybe the generator going out so I flip the belt off and it still had the noise. I mess around with this for days trying to find the source of the sound. I asked my friend at a Porsche repair shop if he had any ideas what it might be causing the sound. He said to make sure the rub block in the distributer was greased or it would get hot and chirp. Sure enough, I forgot to lube the cam block for the points. A dab of Bosch grease on the block and the chirp was gone.