After several weeks passed, I went to Ventiler because I asked Ventiler to install the exhaust manifold.
The following photo is the existing ex-manifold.
As compared with the existing ex-manifold, "COX" exhaust manifold can be flowed faster, as you can see.
After installation....... I could not take a photo !! Can you see the ex-manifold ?? :D
The exhaust manifold smells like burning during drive. But after several days passed, it does not smell.
Regarding the impression, it is VERY good ! My English is poor. So I cannot explain it.:-(
Anyway, I think that my Golf got more power. Anyway, I recommend the replacement of the exhaust manifold !
Regarding the sound, it became noisy slightly, I think.
It became so fun to drive my Golf ! ( Anyway, I hope that it will not crack ! )
Thank you so much, Ventiler !