Looks to me like your fuel line may be picking up too much extra heat at the cowl where it looks to be close to your headers. Since I don't see it, I am going to assume the electric pump is mounted near the tank. Running both pumps shouldn't cause the problem you are describing since the carb will only see the pressure that the mechanical pump can put out. One way to fix it is to install a return line from the carb to the tank. This will keep fuel flowing in the line constantly and it won't have a chance to boil. Another way to fix it is to install a smaller fuel line which will do the same thing as a return line. My personal favorite is to run the tank line into a cool can mounted under the horns, from the can to the mechanical pump, and add a 3/16" or 1/4" return line. Fuel boils at a much lower temperature than water. Also remember that steel lines do not absorb heat as fast as aluminum. Never had a problem yet with that setup, even without ice in the can. Hope this helps.
