The 135i of course has meth and race gas. The VT2-625 setup is likely somewhere in the same area power wise but is heavier. It is hard to know exactly what pulley or fuel the M3 is running.
Oddly, this RB stock housing turbo upgrade does much better against a supercharged DCT M3 than the Vishnu single turbo upgrade 335i posted a couple days earlier did. How does one explain that? Either the Vishnu single turbo is not as strong as portrayed (quite likely as customers are not replicating Vishnu's own hand picked results and figures) or the other M3 in the video is stronger than this one.
For the M3 to pull it looks like it needs a custom race gas tune and another psi of boost. Regardless, great race, enjoy.