tech4me

I basically used your approach, but instead of cutting the wires I destroyed the connector. I superglue the clip back together, hopefully it can last a while. At least now I know how to disconnect them.

Thanks for you replay. I searched for an under-hood picture for your car, and I don't think it uses the same connector as mine.
I FIGURED IT OUT!
I broke one of my connector when I was fiddling with it with a screw driver(I broke the while plastic into pieces by mistake)  At that point I decided to destroy the connector so I can reverse engineer the inner construction of it. After some careful inspection, I found the solution: you have to push the white clip to the outside position and press the white clip and the black plastic under it and the same tile REALLY REALLY HARD, and pull the connector out while doing it.
Thanks again!

The same connector is also used at few other places in the car I think one next to the exhaust manifold and one next to the engine air filter casing. I've tried push every piece of plastic I can, use a screwdriver to poke around. I spent way too many hours on this, at this point I am will to go to a gm dealer and pay them to see how they would unplug this connector.
 
Maybe this extraction tool is required? Even if I get this tool, I wouldn't know how to use it.
https://www.automotive-connectors.com/walter-schroeder-121071-extraction-tool-for-kostal-mlk-1-2-with-protective-cover.html
 
You can tell this is a German connector. It is so over engineered, maybe it is little bit better compare to other connectors spec wise(water vibration resistance). But it is so not intuitive and probably very costly to replace.
 
Sorry about all the negative emotions, at this point it is just frustration. (To rub more salt to the wound, I am an electrical engineer. Although more on the computer side of things)