I have a Gibson furnace with air model GB3BM 036K BB that I would like to hook a C wire to in order to power a wifi thermostat. I wanted to confirm the correct place to grab the common from within the furnace. If I am correct, it looks like the Gray wire coming off of the transformer since the red carries 24v? The be honest, I am not sure what the 2 wire red and white are connected for since only the 4 wire comes down to the stat. I need to get in the attic and see why the previous owner hooked that up. Thank you for the help.