I've been skeptical of these until this last weekend when I watched one keep pace with a friends Shelby GT500 going around Firebird west, and his Shelby rides on coilovers, watts link, Wilwoods all around, 590rwhp. The BRZ wasn't stock either but I doubt it makes more than 220hp. Bigger course would have been different but it was still impressive to see him keeping up.
Congrats!!