Subaru sti N14

I got asked to sort out wiring for a Subaru Sti N14 rally car. Its a prodrive built car , has a Pectel plugin ecu etc.

The car has a lot of electrical gremlins, intermittent faults etc. The cars is originally a rhd jdm sti but has been converted to lhd , so all wiring is altered to make that fit.

i am now in the doubt of removing all , fitting a pdm and setting that up. Or going over everything and repair/improve whats in it. my main concerns are the communications between modules and all the extra's it has:

wheel speed is coming from the abs module which reads the 4 abs signals. wheel speed is necessairy for the ALS. The car has a separate central diff controller etc...

everything is connected so separating the engine loom wont be an easy thing to do.

Anyone on here who has experiene ? i'm not into subaru's normally

This really comes down to cost and time, and how much the customer is prepared to pay. If I was in your situation then my preference would be to rewire the engine side of things from scratch so you can guarantee the reliability of that sub system. It can seem like a good idea at the time to try and save an existing harness that has some reliability issues but that can often end up costing more. The other issue is that as soon as you do anything to it, it's your reputation at stake and you're usually on the hook for ongoing issues. I accept that the integration between the various systems may prove tricky but it shouldn't be too difficult.