There should not be more then a 25% variation between cylinders. If it is well and truely blown there will be very little comp in that pot if any! Others will be from 120-170 depending on the state and type of engine.

And if there is 1 pot with low comp, run the car for a while untill its warm and the cooling system is at max pressure. Then turn the car off and wait 10mins. Now take all the plugs out and get somebody to turn the car over while you hold 1 big peice of paper/clean rag over all the spark plug holes. If it is blown water would have seeped into that cyl in the 10mins and then be blown out onto the paper/clean rag. Then you can see it and be sure of the problem.

What type of car is it? You mentioned late modle EFI.

Chemiweld would probably do SFA to a blowout that severe!