I have a 93 Stealth ES and am wondering if you can get a single coil pack. For the past couple weeks, my car hasn't ran like it used to so today I started pulling plugs and noticed that the back coil pack (the one farthest from the radiator) isn't firing as good as the other 2 packs. So does any one know if you can get just one pack or even if I am right in thinking this could be the problem. Thanks.

Unfortunately Mistubishi doesn't sell individual coil packs. You'll need to get the entire plate with all three coils.

Ok but am I right in assuming that all the coils should be firing equally at the same time

Coils should fire sequentially, but yes, equally.