Don,
Bleed lines burnt through, awhile back I had the same problem on my old mod'd 225 EFI motor, now it's happening again on my mod'd 250 EFI motor.
It's always at the bend in the tubing as it exits the cylinder side of the block on # 1 & 3, what's causing that ????????? It's all new tubing as well. I seems strange that it's happening again on this motor. Both motors were totally set up different from each other.