I had the same thing with my 83SC. I ordered a coil but they were out of stock, so I put in a Bosch GT40 coil that I had inj my parts bin. It has performed well for over a year. I carry a spare in the trunk just in case. The order was cancelled after I did a post on the subject and others reported that there new OEM coils were failing quite regularly. I'd keep the Bosch CDI and just get a couple of replacement coils (keep one as a spare). Others reported that the Blue Bosch works OK. BTW the former mechanic warned me off replacing the ignition wires with after market ones. He said to stay with OEM as they were really good quality (others may disagree though). I emailed a mechanic at a Porsche dealership and he said mixing coils will "TOAST" your CDI. I have to disagree though.

I always carry a Condenser,Stock blue ciol,and tools to convert to standerd points ignition incase of a bcdi failer.Cheers