Perhaps I'm remembering my RAN FAA Vampire time. I don't recall knowing about the above engine modification at all; while perhaps it was not the RAN/RAAF students province to know. Anyway I enjoyed my total Vampire time even though it was short. Macchis were MEH. :-(
You may recall the loss of an RAN FAA Vampire at Laverton with both crew RAN with a RAAF passenger dying in flames at the end of RW 18 because the engine failed during take off with a full drop tank load. That was right at the start of ground school for No.67 Pilot course Oct 1967. Details can be uploaded if required. The RAAF Pax was an engineer due to start the No.67 Pilot course (we found out later).