The fuel in the log is "boiling" because of the combination of three things:
high ambient temp, engine bay temp, and slow fuel flow because there is less fuel flow through the secondary fuel bowl than the primary.
The secondary idle circuit is not supplying the motor as much as the primary.
So, how about feeding the fuel log from the rear, or fit an electric pump with a bypass regulator and you'll always have cool fresh fuel at the inlets.
