In a nutshell, the factory turbocharger (is20 or is38) is very small, and designed for efficiency. The way the boost is controlled is very advanced, with both the waste gate and diverter valve working in unison for optimum performance. Our tunes take advantage of the way the ECM controls these functions, and really breathe life into the car. With our methods of control, you may encounter some "flutter" or "compressor surge" at high-load, low RPM conditions. This varies depending on the individual car or mods such as intakes or inlets etc, but in some cases is completely unavoidable. We have done our best to minimize this condition with smoothing out the boost curves at high-load and low-rpm areas of the map, however some users may still encounter it. The easiest solution for this "problem" is to not lug the car around in too high of a gear at more than 50% throttle input. Downshift to a lower gear, then give it the beans to your heart's content.Note that the flutter is not detrimental to turbo operation.