Hats off to Dave @ Gintani Australia.
Even though my client did not end up going through with the purchase, Dave was more than helpful in providing useful information and honest recommendations on suitable products.
It helps when he has tried and tested the typical range of M3 exhausts and hence can safely compare the Gintani against Eisenmann, Remus, Akrapovic, etc.
Also very assuring considering how particular Dave is with his own car, so you can trust his judgement. He doesn't have the "sales pitch" tone and is very easy to deal with.
I would highly recommended Dave to anyone looking at E92 M3 upgrades