From sources I can find, they genuinely look decent.
I would however note the Watergate pipe looks quite small and is extended. The length of the pipe adds resistance as well as the diameter. Personally, if you buy it, I'd spend a bit adding a wastegate flange on the Y branch location where the twin feed joins the gate. Ensuring the bigger surface area possible therefore allowing maximum flow.
I also prefer a top side wastegate location. I cut and relocated mine. So no jack the car up or ramps just to get to the wastegate.
I've had boost spike issues on my T61 at 400hp and modified my manifold to resolve the issues successfully, now adding flow to 500hp, still without issues.
I think it would be fine but do advise a few modifications to improve it in those areas.