As I understand it the N269 is there to stop too much boost running through the standard Bosch DV, which uses a very weak diaphragm as opposed to a spring design, prone to leaking under high boost.
With many people remapping their cars and running higher boost levels they are advised to upgrade to a stronger DV - and when this is installed it makes the N249 redundant. If you look at the route of the vac pipes it also means the air has to travel much further between the dump valve and inlet manifold, making DV response quite laggy compared to running a dedicated line between them. Another benefit of this includes a crisper, sometimes louder dump as well.
The SAI is only there to meet US emission regulations so by getting rid of both N112 valves you can clear up all the clutter on top of the engine, while also reducing the risk of a boost leak by removing countless vac pipes and unnecessary valves (including PCV etc)