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I have another carb which I took off another B2. Looks the same but this one has access to the idle mixture screws. My current carb has the screws sealed over. Should these carbs be interchangable. What does the electric gizmo attached to the back of the carb do ??? Thanks for the training lesson Bob

You should be able to swap out those carbs.

The gizmo on the back is a metering rod. It adjusts fuel mixture based on feedback from the O2 sensor. If it's unplugged, it defaults to open, and gas milage will suffer.

Thanks for that info, I have a rough idle condition when the truck is cold, it improves when the engine reaches operating temp. I have adjusted the choke and the choke plate unloading valve to what I think is correct and the truck starts great just that it idles rough for a few miles as stated above. Based on exhast pipe condition I am thinking it is running rich on fuel and because I can't adjust the mixture maybe I should be looking at what the 02 sensor is sending to the computer brain and then to that mixture valve or just unplug it from the get go to see what happens ??? Being a shady tree mechanic is so much fun