I bought one of the Exhaust manifolds shown but a HKS brand for $550 off SAU forum advertiser and it took two months to get it. Thought I had been dudded but got it eventually.
I fitted it along with a lot of other mods so cant say the difference it made but it has not cracked so far, but then again the car has been off the road a lot anyway.
The dyno results talked about do not reflect the on road drivability that this type of manifold might provide in comparison to the standard item.
I know we have to try to measure everything for comparison, but a dyno cannot tell the complete story regarding real world on road driving experience, and I dont drive at WOT everywhere in the city!
I am sure it somehow contributes to the efficiency of the power output and hopefully will know very soon after a dyno session with Dr. Drift now that I have replaced my faulty knock sensors.