Thanks for the pointers. What makes the car go again is if I hook the fuel distributor up to a Sun MotorVac and run it through the system (engine off) for about 15 minutes. The car then runs fine for a few hundred miles, then very rapidly goes rich again. Has anyone seen this problem?

The fuel consumption increases dramatically when this starts to happen, so it runs really rich until it's put on the MotorVac. So if the fuel system pressure is in spec, what could cause this?