YOu said no compression but you said it's sucking air in the exhaust.. This is a clue. Story or two (2nd one short)
Reading Gus Wilson's Model Garage (Series in popular Mechanics) back in High School he had a car brought in with what they thought was a blown head gasket. Well he confirmed two cylinders not working and as I recall it was the intake valves. or perhaps I'm mixing the two stories it was the intake)
He screwed a spark plug housing with the plug broke out and a air chuck brazed in into the spark plug hole and put compressed air to it and noted where it came out(I am confused it was a blown head gasket, Radiator bubbled)
My car it was the intake valves (That's how the mechanic figured it out)
Sounds like the exhaust valve on yours based on the sucking (the power stroke)
