From what I've read is ether destroys the precups on the heads, and in general can break a ring. Breaking a ring most likely won't cause it to chuff like it is.
I'd still start with compression testing, because if that one hole is way off, or really close in reading to the rest of the holes, it'll tell us if it's a compression issue or something else.
Is it possible it is compression from broken rings coming up through the cdr? This was why I ask about blowby from oil cap, compression in crankcase should be seen out the oil fill every time that cylinder comes up on compression.
If the valve train looks good, pinpointing cylinders would be next. Another thought I had, if it seemed like it was running on all 8, but just wasnt right, is headgasket between cylinders.
Can you post a video of cranking with FSS wire disconnected?
This is also very possible.
I would pull the oil cap and spin it over before spending money on the compression tester to rule out compression into crankcase.
If there is compression from oil cap that would most likely mean some sort of piston damage.
If no compression from oil cap I would try blowing air into each cylinder with valves closed.
If there is one cylinder that blows back to the intake, I would lean towards valve.
If two cylinders next to each other blow to intake or exhaust, I would say head gasket.
This is my thoughts, which may not be worth much, (I am what most call a shade tree mechanic) so feel free to let me know if any advice I give is counter productive.
James