If you know for sure that the lower intake is the source of the poor idle, yes, you are going to want to change that ASAP. But make sure it is, because it's a job that you won't be happy if you do it and the problem is still there. Not even sure where to begin on a rough idle given the info that we know, a good starting point I would recommend is tune up - cap, rotor, plugs, and wires, then go from there.

You can bypass the inertia switch, but remember that the fuel pump isn't going to turn off in an accident. Really your call. It's a switch, so bypass is strait forward. 12v so make sure there's no way that power can contact ground.