Got my Berks fitted at the weekend and complement the Nismo fantastically. Definately a rasp 4k-6k revs, but it sounds great.
Adds great depth of sound to the mid range, made me think that I might even pop the original exhaust back on with them, should I want to raise some cash by selling the Nismo.
All in all, a great product.
Only time will tell, but interested to see if the noise changes as they 'bed in'. If you have a loud exhaust to start with, these will definately take it to another level!