I know faulty plug wires will arc out and fail under a load on a hot day. If you haven't had new wires within 60,000 miles it would be good to replace them. But, if the problem is heat to the ignition module I agree with you. Mount it in an airflow someplace. If that can't be done because of the wiring you could run some fabric duct tubes like are used for the air flow under the dash from the outside air in front of the engine to the ignition module. I have used some of that type of material to run a cold air intake to the throttle body of my car. It works well.