There are 2 turbos though, a TD04-15G and a TD04H-15G, and the two have different housings. The vr-4 guys use 15Gs as an upgrade very often. It has a pretty proven reliability and is good for mid 11s with the right setup. They will cost you probably $2200+ though.
That link I gave you MIGHT have a compressor map for the 15G also.