There is also the issue of all the weight in front mounted turbos being on the front end of the car. I liked the idea of the STS kit distributing the weight a bit better over the entire car.
Personally, I have never really noticed any notable lag with the STS. I guess if you just tromped the accelerator you would feel some sort of lag, but if boost comes on at 3500 rpm, I would think boost would happen regardless of how quickly the engine gets to 3500 rpm. The engine is moving the same amount of air at that RPM level no matter how you get there. And since there is already an air column in the pipes, it's not like the forced air has to suddenly fill a vacuum.
But I guess since air compresses, that perhaps that could be what is happening to cause some sort of lag. I just haven't experienced that myself, but perhaps I don't tromp on the accelerator all that much.
Beats me. I've always been happy with the system myself.