Was the bulk of the tunnel pipe insulation encroaching on something? If I was running my coolant through the tunnel (one of the first decisions I made with my build was to run it outside of the cabin), I'd be applying multiple layers of a ridiculous amount of insulation. The main complaint I see with driving a finished GTM isn't the harsh ride, isn't the deafening noise, isn't the blind spots, isn't the chore of getting in and out. It's the heat off the tunnel.