Lately when I've been driving, I've noticed my idle sitting at 300~400 revs, which is about half what the owner's manual says it should be at, and the car feels like it's about to stall at the lights. Also, driving along, the car feels gutless, like, you could put your foot down, and the revs will rise VERY slowly, but the car will pick up speed reasonably quickly. Could this be an electrical problem? Like leads or something similar?

are all the spark plug leads firing?

It could be the ICS.....mine just died this week and had the same problem of idle at less than 500rpm and stalls......

Could be electrical, maybe a dieing battery?
Also i cant see how your car is dropping to 3-400 rpm, i thought our engines stall if they drop below 500, i know mine does.

Might look like 300-400 rpm on the tacho, but probably isnt. I would question a tacho's accuracy at revs of that nature and also the tacho (at least in mine) is non-linear from 0 to 1000. Hard to accurately read anything under 500.