It's usually referred to as the crank sensor or flywheel speed sensor, and is situated on top of bell housing. You can see it when you remove air box.

Job is to signal to the LH that engine is turning, signal TDC and relative crank position. In absence of signal there's no spark.

Signal from this sensor also feeds the rev counter which aids diagnosis of crank sensor failure (needle doesn't move).

It often fails around 20 years - in particular the connector crumbles. Won't run without it!

Where from Paul and do you mind saying what it cost?

It's expensive via Porsche but I can find the Bosch cross-reference code for it, and understand it's a lot cheaper buying via Bosch channels.

Am bound to need one in future so good to be prepared.

Good find then!

I am downloading PET7 now.... tis taking forever, but nearly got 3 of the 4 files. Hopefully it will work when finish downloaded. Good find Brett,

Regards
Paul