The Fel-Pro O-ring is 1/8" cross section and is too large. I have a chance to work on another E46 today and can see how the O-ring will roll. I believe that 3/32" cross section is about correct, however, I have some more parts coming soon and will verify for sure. Then I need to see if I can easily source a part that can be picked up at a local parts store easily.
Also for everyone to not, you need to also check carefully that the DISA vacuum accusatory diaphragm is not blown.
I have updated the beginning of the thread with update/pending O-ring info and info on testing the DISA vacuum actuator.
Apologies to anyone regarding the Fel-Pro part, I should have verified personally.
Again, this thread is a work in progress and feedback is welcome.