After operating perfectly for about 3 weeks, my '90 325is had another fit with searching idle that stalls out, stumbling at speed. Gives 1222 code. (The code had cleared before.)

Cannot see any obvious bad vacuum hoses or connections, so I think maybe I should just replace all vacuum hoses, for starters. Can I get hose stock from AutoZone or some place? Or do I need to buy BMW parts?

If it turns out to be the intake manifold gasket, is this a DIY for someone with moderate skills and experience?