Hi,
When you remove the hose, you are creating a large vacuum leak. That is why the engine runs really poorly. As far as testing, the brake booster is a vacuum operated device. The way to check them is by applying a vacuum to them with a vacuum pump (with a gauge) and seeing if the pressure drops.
By chance, have you tried checking if there are diagnostic trouble codes? Also, there is a vacuum pump mounted on the booster. Do you notice if it is working?
Do me a favor. Take a look at the picture I attached below. Let me know if that is what you are seeing on your truck. I ask because based on your description, it sounds like you have a vacuum assist brake booster. However, they also used what is called a Hydro Boost system on some of these. Brake assist is done by the power steering pump.
Let me know.
Joe
See pic below.
Image (Click to make bigger)
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Monday, November 27th, 2023 AT 8:37 PM