STS is a remote mounted turbo system, meaning that it is located away from the engine. Usually these are mounted inline with your exhaust under your vehicle. The good part is they are easier to install, the bad part is that the turbo is exposed to anything and everything you may drive through!
Yes it locates the turbo down near the rear axle. Not an issue if you stay on pavement....most that do turbo wouldn't dare take their truck off pavement anyway....but good point it is something to consider...