Tips for wireing harness removal

[carltalon]

Im in the prossess of removing my engine wireing harness so I can add in the wires I need for the auto swap and do some tucking to clean up the engine bay. I have the harness removed from the motor batery and fuse box under the hood. I also have the harness unhooked from the ECU.

My question is. How do you get the harness through the fire wall? it looks like it goes behind the heater core then through. Is there any way to get it out without removing the heater?