Keep in mind that fire sleeve's main function is to protect the contents from flames, not to reflect heat. In fact, once the engine compartment has reached a steady temp, whatever is in the fire sleeve will also be at that temp, and that's the problem. These cables that Vans sells are basically made for boats. You might want to consider also wrapping the cable in reflective heat tape and using exhaust pipe heat shields to redirect radiant heat away from the cable as much as you can.