[RETed]

Some options...

Electrical OMP:
Keep the S5 harness already installed.
Plug the E-OMP into the harness just to fool the stock ECU.
The S4 mechanical OMP is just going to operate normally, since it has nothing to do with the stock ECU.
No need to mess with a messy front oil cover swap.

Boost sensor:
You just need to repin the plug, since the only difference between S4 versus S4 boost sensor is a +12VDC reference.
The other three wires are +5VDC, signal (back to stock ECU), and ground.

Fuel injectors:
You can run the low-impedence fuel injectors just by swapping plugs - easy to find EV1 / Bosch type and installing resistors on each channel.

Alternator:
Only difference here is I think the lug on the main power wire to battery?

Main engine harness:
This is where is gets tricky, since it doesn't plug in with the dash crossover harness.
This is where you gotta repin or just brute splice the wires to make everything work.
This is basically just to get the instrument cluster working (i.e. oil pressure, boost) and wipers to work.

As for the turbo, the S5 has a longer "adapter" pipe on the front from the oil pipe drain from turbo to the front oil cover.
Else, the positioning is identical, although it looks physically different - due to the turbo clocking.


-Ted