intake manifold heat riser

I drove VW bugs for many years to save my mopars in the salt belt. Under certain conditions when it was cold and damp, the carb would internally ice to the point of stopping the the car. The small exhaust tubes bonded to the intake did not provide enough heat transfer. It was less of a problem in town, at low speed where the engine heated the engine compartment. It was a problem cruising at highway speeds.