Could it be a overheating coil..?

You'll always get some of that if your pump is weak. As the needle valves open, fuel is allowed into the carb draining the line. As soon as the valves close (because the carb bowls are now full) the filter will fill again. I had this problemn with the old stock pump because the diaphragm was being eaten up by the new crap the pawn off as gas. I'll bet you also see a bunch of black crap floating in the filter.
I installed a new stock filter with a diaphragm designed to work with the new gas and voila, no more black crap and much less air in the filter.