Hi,
I just spotted your post - must have missed it since there is so much stuff put here daily!
I dive a modified IDA-71 and am quite happy with it. It is not very expensive or complicated to build and dive it. However, there are limitations to the unit.
As others have said before me, there is no water trap and the exhaled gas passes through hoses in the breathing CL. You need to be very careful in what you do. If you manage to get your hands on a unit, there are plenty of people that can steer you in the right direction wrt mods.
Before you start modifying and toying with RBs you have to realize that in thiis "game", mistakes can be fatal.
If you want to see more on the modified IDA I have, please visit these links:
http://www.kamarinos.com/rebreather/IDA71.asp http://www.kamarinos.com/rebreather/IDA71b.asp and
http://www.kamarinos.com/gallery/
Cheers,
George