Vega 64 doesn't function nomally (decreaded performace) on my AMD Ryzen platform Hackintosh

My configuation:

GPU:Sapphire Vega64 Limited Edition (Silver fan-cooled)

CPU: AMD Ryzen 2700X

Motherboard: ROG B350-F

Memory:DDR4-3000 48G

SSD:WD SN720

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System information

The GPU seems to have been initialized normally.

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System information

As you can see, the geekbench OpenCL benchmark only get 40000 which is far lower than its normal score (about 200000), and the Cinebench 15 only get 70fps.

Geenkbench OpenCl Score

However, on windows 10, this card get the normal score

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And when I run the Metal benchmark on Mac os, it seems to get a satisfying score.

Geenkbench Metal Score

The fan is silent, functioning normally without pathing anything.

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I have tried to fix it, including

1. remove whatevergreen and lilu - ending in failing to boot
2. update whatevergreen and lilu to the latest version - no effect
3. enable RadeonDeInit - no effect
4. use kexts to adjust the fan and voltage etc. (like VGTab) - no effect
5. update the system from 10.14.1 to 10.14.5 - no effect
6. reinstall the system using AMD-Vanilla - no effect
7. switch the model from iMac Pro to iMac or Mac Pro - no effect

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Here is my EFI

https://drive.google.com/open?id=1xnXdBBtukPjcEP2WfbUW081niPKlWMEs

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I have searched the internet but can't find a solution any more. So I turned to you to help, thank you~