I have been running that Cool Carb heat shield and two of their spacers for 2+ years now on my 340. It definitely helps but you have to make sure that you have the crossover blocked! The Cool Carb has a max temperature range around 250-275 degrees (I forget the exact temp per CC). It will melt above a given point! BUT,,, I have an aluminum intake with the crossover blocked and I have not had any issues! I have noticed that after driving around and allowing the engine to idle, I can touch the carb and it is much cooler than I would have thought.
This is not a miracle part for the crapty E10 gas that has been handed to us but it is definitely a good upgrade and I will not run without it. Good product!