OK I couldnt figure out how to make Reaktor work as an AU within EigenD properly as the parameter list contains hundreds of seemingly useless options when Reaktor is used. So I will recommend using pico as midi controller when wishing to use it with Reaktor.
The procedure:
Make sure you have at least one IAC virtual midi bus setup via OS X Audio Midi config utility.
Use the browser & pico to set EigenD to use the IAC midi port
Switch the pico to play instrument 8
Load reaktor and make sure it is set to listen to midi on the IAC bus
Load the SIlverwood patch into Reaktor
The Silverwood is listening for midi breath on a different midi cc to what the pico uses, so the patch needs slight modification, you only need to do this once and can then save the modified Silverwood:
In silverwood, look for the dropdown box labelled 'Air Source'.
Right-click on it and select 'Show in Structure'
You are now looking at the internals of the Silverwood patch
On the left there are 4 Controller patches below one called Air Source
Click on the second of the controller patches
We are going to change one of its properties so make sure you can see a window called Properties, press the icon in the toolbar that looks like a hand pointing at a card if you cannot see it.
Now in the property window click the icon that looks like some gears
In the midi section that appears, change the number in the controller/note box so that it says 17 instead of 2
Now press the toolbar icon that looks like some faders, to switch back to viewing the Silverwoods main controls.
Blow into the pico pipe and press some keys, you should now get a result.
Save Silverwood
If you see another control in Silverwood that you would like to control with the Pico, right click on it and select midi learn. Then use the appropriate controller on the pico, eg bending a key to the left.