I just installed the RZY harness on my truck last Friday. It took me a solid 5 hours to install mine. The whole harness doesn't have to go thru the firewall, its just 1 wire(the purple wire) and I took a small piece of tie wire and stuck it through rubber boot at the firewall from the motor side, taped the purple wire to it and pulled it through. Another tip is if you plan to disconnect your battery, which i did, make sure you move your driver seat all the way back and your adjustable pedals all the way in so you have the most room in the footwell. Its all doable, you just gotta have patience because all the spaces are very tight. Good luck!
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