I bought used when I helped Tom with his SC install. It has a throaty sound, but not all that loud. I can hardly hear it with my Brullen exhaust makin all that racket.
Not too sure about power increase, last time I drove my car it was not tuned properly yet and running way too lean. It runs very strong now, but I have to re-phase my intake cam and e-test it to update the plates.
BTW- If anyone wants a K&N drop in a 12 of beer (Keith's please) is my price.
1997 Z3 with N/A power adders....