i have the exact same problem. The part you took a picture of, I believe is like a vent for the manifold. Pcp? I dont think its a vacuum problem. I have a **** load of parts coming today, coil, reciftier, everything that it could be, I hope. Let me know if you find the problem please. I'll do the same. Watch this video. I did all the testing the guy says and I know I have a few bad parts .
https://www.youtube.com/watch?v=BSZ3t_oibeA