Those three vacuum switches control air being pumped to either the exhaust manifold air ports or downstream to the catalytic converter (and one other function I can't remember at this time, possibly the air filter warm-up diversion?), and should be no longer in use when the ECM is bypassed, like you did with your non-computer BBD carb swap. If you want to leave the system in place so it looks stock, but doesn't introduce any possible vacuum leaks in an otherwise non-functional system of hoses, you can plug the line from the intake with a piece of dowel, then reconnect it, so its there for show. The vacuum can in the fender has a tendency to rust out and become a hidden major vacuum leak. Its funny, the can looks like the AMC engineers just used a coffee or juice can from their break room, and carried that into production.