Ok, I should mention that I asked, zombie84, if he could check if the book "Skywalking" by Dale Pollock mention anything about the studio interference on THX 1138 and he was kind enough to look into it, here's what he found, not much but very interesting:
It says on p.97 how Warner turned the film over to in-house editor Rudi Fehr:
"Fehr cut only four minutes from THX, mostly scenes in the White Limbo and some of George's bizarre attempts at humor."
Thoughts?