The engine loom is the part that is going to affect the running of the car, that and the fuel pump wiring. Run a new feed to a new fuel pump relay and drive the relay from the original fuel pump relay. If your half decent with wiring you should be able to split the engine loom from the rest (think theres about 5 wires that actually pass into the cabin) and make a new one up, Im in the process of doing mine as 19 year old wire isnt what it used to be!