Just a quick follow up:
Tim Brierley and I went down to see Ergen Motorsport to see the M54B30 running on a standard MS43 ECU, but modified to run outside the normal E46 chassis. We had a very useful discussion about what Adem does, how he achieves it, and how he could help with Tim's M52TUB28?
Adem is clearly very knowledgable about BMW ECU programming and wiring, where he has obviously found a niche. He had several very sporty BMWs with engine transplants in his workshop, and clearly knew what he was doing.
As agreed, he had modified my M54 wiring loom and ECU, to make it literally 'plug and play' in my Cabrio. Interestingly he had retained the EWS for added security, removing only the CAN bus requirement to communicate with items such as instrument binnacle, ABS and a few other items that do not appear in my Cabrio: everything else remains totally standard.
This is the business end:
With modified MS43 ECU (to run the M54 without CAN bus, instrument binacle, ABS and various other items not on my Marlin chassis), but includes syncronised EWS, Key/Antenna, Drive by wire throttle and X20 connection to match my existing M50 X20 connector.
The X20 connector grafted onto the M54 wiring loom to make it Plug and Play.
The top part of the loom is standard with all the necessary connections to the engine sensors etc.
The whole loom does not look too bad when laid out like this - the top section all goes to engine connectors - just a case working out which is which! - and the bottom half requires the X20 connection, the BMW key to be close to the Antenna, plus a live and Earth, so even I can manage that!
My plan is to test my M54 engine alongside my Cabrio before installing it, by plugging the new X20 into my Cabrio's socket, then add a few strategic Earths and a mains supply to the starter motor, and divert the fuel hose across from my Cabrio chassis, and should then be able to start the M54 from the ignition in my Cabrio!
It sounds almost too simple to be true, but provided I get my wiring connections right, it should work.
Tim had a good chat with Adem about his M52TU, and it appears that the same wiring loom for mine will provide Tim with a loom which works.
Tim left with arrangements to take his Sportster along to Adem to make a proper assessment.
A very worthwhile day out - quite exciting for both of us