Various things have come up -
A document dated March 45 showing the 'intention' to use 1.98ata for ALL K4 units.
A document dated end March 1945 showing them still using the B4 fuel, so no 1.98ata.
So you would have to believe between the end of March 45 and the end of the war in ealry/mid May they managed to convert them.
Bearing in mind the C3 fuel required for them was scarce, and allocated to the 190 units anyway.
It has a been a big bone of contention.
Got a feeling I know where the 78 came from.
Same guy who has been trying to prove K4's used Flettners also, despite being shown they were ALL locked shut on K4's.