It is hard to picture where this line is but I suspect this is an EVAP line if it is a larger line.
However, it could be the brake booster. Basically we attached the info below on the manifold.
No matter what I would make sure you check for vacuum leaks when you get the engine started.
These leaks are the worst to try and figure out so it is better to check even if the engine is running well.
Please run through this and let us know what you find with this.
Images (Click to enlarge)
Friday, September 3rd, 2021 AT 6:24 PM