
(I've also kept it somewhat documented here, but I don't pretend that wiki is otherwise active)
Two parts are pretty easy to adapt: VAG 058905161B and Bosch Motorsport 0232103037. I'm using the latter, but I did fit the former previously (didn't finish the rotor adaptation on that one). I'm pretty sure you could fit a sensor to the rear of the cam too, I've seen some 911s do this with a bolt added to be picked up. That does your adapter seal against oil though, so this is easier...
Anyway, VEMS requires a masking (or really, inverse mask - so allowing?) pulse generated by the cam sense circuitry for their "auditrigger" trigger architecture. If you check their schematic this is Q13. This means you can't have an arbitrary phase offset, the pulse needs to be squarely overlaid with the TDC pulse from the reference sensor. So, I stuck a bolt in the rotor, measured up the angle at TDC, and printed a bracket:
And, well:
Some help parsing that:
yellow: width of cam sensor pulse, 13.74ms
green: period of cam rotation, 113.67ms
magenta crank rotation 1, 57.87ms
orange: crank rotation 2, 55.91ms
purple: desired shift of cam pulse, 8.86m
Not sure why, but that didn't line up. Probably to do with precisely where along the face of the sensor it triggered, but even that doesn't account for 30 degrees! That's a lot!
Anyway, shifted it by 28 degrees to land the crank TDC smack in the middle of that cam pulse, reprinted (forgot to take a picture), and:
Perfect

Just finished making the modifications to the ECU to support this - basically needed to swap some inputs around and solder in a single NPN transistor that masks the TDC signal unless the cam signal is also present. Will test it probably tomorrow, and hopefully document the VEMS configuration differences required (basically just doubling of teeth and rearrangement of the tooth trigger table for now - I don't have a harness in place for sequential inj/ign).
Of course I'll be sharing the models and some general directions once I know it works to...any standard.