When we were developing the Stage 2 Supercharger kit, we found that air/fuel ratios were not being consistent. This was very strange because we hadn't run into that problem on our Twin Turbo kits on the 370Z or any of the earlier VQ cars we have Forced Induction Systems for.
We did a lot of digging, data logging and testing to find the root cause of the issue. You see, on the 370Z, Nissan changed the wiring to the factory fuel pump wiring harness. On the stock fuel pump it's no big deal and in fact the older Z's and G's were a bit overkill on the wiring side of things. What we discovered, was that voltage was dropping when the fuel pump was working the hardest and drawing the most power. We developed our Fuel Pump Voltage Stabilizer to make sure that the fuel pump gets the voltage it needs to operate properly all the time without having any fuel delivery issues.
It has been alluded to in the past as to why this isn't an issue on the twin turbo cars before, but I'll go over it again just briefly here. Twin Turbos do not consume horsepower in order to produce positive manifold pressure the same way that a supercharger does. That means that in order to get XXXwhp from a supercharger, you need XXX + the amount of power the charger consumes. As such, there is significantly more fuel demand on a supercharged car at peak power than the equivalent power turbocharged car.
Now, you asked "at what point" it is required. The answer is "it depends". On our supercharger kits, if you are going for 480+whp, it's a good idea. There may be cars that have a lower threshold than that, and there may be cars that can tolerate more power. There's a lot of variables involved, but we take the stance of "better safe than sorry" with this and include it as part of our Stage 2 Supercharger kit and highly recommend it with the Stage 1.5 system. It is also available on its own for those that purchased systems from other companies that don't take things quite as seriously as we do. Remember, we don't just make a kit, we engineer the whole shebang to make sure that no matter what power or performance you are after, you have the products available to have everything mesh together cohesively.
