carter carburetor l6 258 WTF did the PO did?

I have a series of problems with my carburetor, the engine dies when going up on incline road it also dies when I reduce my speed or when I'm going down on an incline road if I don't push the gas pedal :/





So I took a look at the carburetor and I'm pretty sure I'm missing the thermostat











The choke plate is always at a fixated position; completely open

Also why is there a copper tighten there? I think its tighten to the choke plate lever or something









What should be connected on this pipe?









I saw on some other post on the forum that the elevation can affect how a carburetor performs, my city is about 2240 meters (7 349 feet) above sea level, over the course of a year, the temperature typically varies from 6°C to 27°C and is rarely below 3°C or above 30°C.



There are only 2 types of gas available

"Magna" with 87 octanes and 300 ppm of sulfur

"Premium" with 92 octanes and 30 ppm of sulfur



however I was told by a friend who doesn't have any source to support his claim that I can't use Premium because my engine would not be able to handle it, how true is that?, what kind of gas do you use?





Is there any hope to make this carburetor work properly or should I change it? If so what would be a good choice?

Fuel injection is currently out of my budged :(