79 c10 vacuum leak please help?

[c10Sleeper]

Hi my name is Kori well until recently my truck was running fine i bought a new master cylinder and booster and had a mech install it when i got the truck back i it doesn't stay running or idle i have to keep giving it gas and keep the rpm above 1500 or it will stall and shut off. i figure its a vacuum leak because of 2 reasons 1 the booster that was installed which deals with a vacuum hose but that hose is secure and clamped to the manifold and reason 2 is because when i give it gas i hear a faint whistle. the whistle is not the fuel pump going out this i know because i just replaced it 20m ago and the problem still persist. plz help any advice is helpful and

[Damon23]

If it is a new booster then the rubber line going to the back of the carb could have a hole in it, the port on the back of the carb could have been broken or the plastic part that goes into the booster could have been cracked (happend to mine) or the booster itself has a issue.

[c10Sleeper]

the rubber line is good i checked no holes or cuts the check valve that plugs into the booster is good i have 3 different ones swapped all the 3 in and out problem still occurs and the booster hose gos to the intake manifold and no ware or tear seems to be on that port i inspected it as far as the new booster having a problem i doubt it because the brakes are 10x better than before. I would try to see where vacuum leaks are with a propane tank but i cant keep the truck idling so i don't know how to find them if that's what the problem is..?
Thanks for the response checked off all your checklist but it none of those as i can tell and the problem is still there

[95 S_Trucker]

Clamp the hose shut that supplies vacuum to the booster. See if it runs any better. Just because your booster is new doesn't mean it's good.
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[c10Sleeper]

Funny you say that cuz i did that a little before you posted that i used vice grips and clamped it closed to stop the vacuum from the booster. Still idled after start and then stalled. I took the air filter off the top of the Carb and took a look i think its the sensor on the side of the carburetor that opens and closes the lip on the last picture i posted. The cover or whatever its called that little plate is suppose to open when throttle is pulled and close when shut off and at idle its suppose to remain a little open.
First and Second picture the part on the carb that controls the plate that's the part i think when bad and i think that's the problem. Third picture is the carb and it shows the plate. The part that bad is on the left side idk what its called but i think its a sensor and its electrical cuz it has a ground and a wire that gos to the fuse box inside the cab. ill keep yall posted let me know if any other ideas come up cuz this might not be it