I have one on my ES, with a cat still intact, and it sounds nice. It does have a noticable drone sound on the highway, so plan on turning your radio up or using some dynamat to help keep the sound out. Outside the car, however, it has a really nice sound.
Performance wise, you will notice a difference, especially in the higher RPMs. One thing I love about this system is that even on an engine such as ours, the system provided a nice pep to the car. I couldn't comment on a turbo application, but I would imagine the same.
My only complaint with it is that I wish that CS would ship it with the hangers bent, so that hwen you get it, you just bolt it in. Also, I have owned both versions of the midpipes, both with and without the flex piping. The solid one cracked in half, but the flex one has held up pretty well so far, although it has a faint look of a crack forming. It could just be my imagination, but I'll keep an eye on it and see if it continues. For the money, I don't think you'll find another system that looks and sounds as good though.
Overall, I'd give it a 7 out of 10.
