Pipe identification help...

Hard to say really, it's used to activate the whole sai pump/combi valve with the n112 pump i.e. on initial cold start-ups so in that sense no, it won't. But if I'm not mistaken the n112 pump also connects to the n249 pump by a vacuum line which runs with the vacuum tank so changing the vacuum could affect the running of the car. Whether it would run lean or not would be difficult to say. Just replace all the vacuum lines under that plate in front of the intake manifold with some silicone vacuum hose or do the n112, n249 bypass.

I think there's two guides on here, just have a search around there's been much discussed on this before.

If your running lean there could be a number of reasons why this is, but again replacing all the vacuum lines with silicone vacuum hoses will help, especially if you have a leak from the vacuum line under the intake manifold to the fuel pressure regulator. This will mean the fpr isn't scaling fuel properly because of a leaking vacuum line, causing it to run lean. That's one scenario and looking at your picture it seems your vacuum line from the fpr to your inlet mani is worn, but start from the above and replace all the hoses, clear fault codes and then give it another scan after a drive then go from there.