93coupe

Well the other day i was pulling out the old ka out of my friends car and we were having trouble getting the wiring harness out. I noticed that it does a big loop it comes out from the ecu and loops around to the drivers side of the car and the runs under the carpet to the ecu again. Next summer I'm going to be swapping in a CA18DET and it comes with the uncut wiring harness now do i have to pull the whole thing out and if so is there an easier way of doing it or what? Thanks for the help in advance.