Our higher compression is one thing, but the S16g or the T3/T4 turbos flow more air per pound of boost than the stock T25 turbos that the GST/X come with. That means that we make more HP per pound of boost over the T25 at the same boost level. The 420A is a sweet engine. After rebuilding and assmebling my engine, its really a damn good design. Very simplistic also.