The fly-by-wire throttle turned out to be very simple, 6 wires from ECU to potentiometer with no sidetracks. I wish the trans wiring was as easy!
Make sure you use the original wire or when replacing a shielded cable. During prototyping the Vencer Sarthe's wiring loom I experienced some serious EMC. When switching the heater valve on, a solenoid, sometimes the lift system was operated. These signal wires of the lift system developed a tiny signal current because of the shock current through the wire of the solenoid water valve. These wires were no way connected and were lying only next to eachother in the same harness part. You do not need an automatic throttle pedal when switching the lights on.
I know what you mean and I think Vauxhall had some similar problems! The loom from engine ecu/trans to the trans ECU contains 2 shielded cables, 1 with 4 wires inside and one with 2. Besides this, the ENTIRE main loom was wrapped in a sheet of metal foil where it passed between the heater assembly and the aircon control panel! So I will definitely be making good the shielding! (even though the aircon and it's control panel will no longer be used!)
Whilst I have your attention, I was wondering about the shielded cables, is it OK to shorten them? I can't think of any reason why not, but I don't pretend to know anything much about electronics (as opposed to car electrics) The wires inside the shielding don't look anything special, just smaller and thinner than the general stuff in the rest of the loom.
On the donor Omega, the engine loom joined to the car loom near the L/H/F strut tower which then made it's way through the L/H bulkhead stopping at all points between till it reached the Trans ECU which was situated about where the wiper motor is on a RHD Dolomite high up on the R/H bulkhead above the throttle pedal. It is MY intention to mount the trans ECU high on the L/H bulkhead, behind the glovebox, which will make all the wires going to it (there are lots) about 2 meters too long! Shortening most will not be a problem, all have been cut at least once to disentangle them from the main loom and all will be carefully rejoined with proper soldered joints and shrink wrap insulation, it's just the shielded cables i'm worried about! I'll probably use the tinfoil from the donor to protect the joints as an added precaution, but is it OK to shorten the shielded cables in line with the other normal stuff?