Could be cam sensor or crank sensor detecting knock and wont let it rev past that would also it would pull the time out of it to protect itself could be loads of things mate I'd try them first
Hello buddy I brought a manifold from America and found it cracked really easily it was a turbo manifold but will be made of out the same metal t304 now I brought one from speed factory which was rather pricey but well worth it hope it helps!!