With direct injection the high pressure needed to inject large amounts of fuel in a short window (that gets smaller as revs go up) requires some seriously powerful fuel pumps. Thus far in the time the N54 motor has been the market (which is approaching a decade) no tuner has delivered a fully functional direct injection HPFP or LPFP solution to support the largest turbo options.
It isn't easy (and tuners are working on making it happen with the direct injection system) but some are going outside the direct injection fuel system altogether. That is what you see here from KS Tuned / Kaizenspeed. Their solution is a port injection manifold which supplies extra fuel. Some may call this a band-aid or not a proper solution but if it works it certainly is much better than no solution at all.
Keep in mind there are cars on the market that use both port and direct injection successfully. The most obvious example is the Toyota 86 platform which is produced by Subaru as the BRZ model and Toyota as the Scion FR-S. This chassis uses a Subaru designed 2.0 liter four-cylinder motor known as the FA20.
Direct injection allows a fairly high 12.5:1 compression ratio thanks to the cylinder cooling effects as well as a leaner tune for fuel efficiency. Working in conjunction with the direct injection system four 205 cc Denso port injectors that supply additional fuel. Essentially a balance between a fuel efficiency design and enough fuel to make power is struck. This same sort of solution may be the answer for the N54.
The problem though is what will control the additional injectors and coordinate with the direct injection system on the N54? Pro-Efi announced over a year ago they were working on this yet thus far no positive results have been shown. CP-E (Custom Performance Engineering) is also working on a port injection solution. Additionally, Defiv is also working on hardware for a port injection system. The problem wont' be the hardware here as much as the tuning to get a system never designed with a dual injection fuel system in mind to function.
Does KS Tuned have the answer? We will have to wait and see. Making a computer model is easy, applying a design in real life is something else entirely. At lest we know more people are working on the N54 fuel system and eventually a solution will be available. The main question being how long is eventually.