Stuck or leaking intake valve or valves. That sucks man! If you don't have the time right now or the patience to pull and rebuild that 6.9, then a running take out IDI might not be a bad idea.......... if it's decent engine.
If you go that route, it'll give you some time to rebuild the 6.9 to better than new.
Either way..... we all would like to see some photos of what happend.
Heath