Ben
Before doing a lot of expensive things, I'd suggest just doing several simple things and go from there. My 02 Conv has about 170k miles on it and one thing I have learned over the last 5+ years is that the 2.0 engine is very sensitive to the misbehavior of minor parts -- especially if more than one are starting to fail.
Therefore, in your case I would suggest spending $50 or so, along with a few hours of your time, and just change the following:
(1) Sparkplugs (gapable ones and set the gap to 0.030" -- not 0.040" or 0.044")
(2) Air Filter
(3) PCV Valve
(4) Fuel Filter
Note: except for the fuel filter, everything else is not difficult to access from the top of the engine... there is a recent post in this forum as to how to disconnect the two fuel filter connections -- down low on the frame on the intake manifold side.
http://www.kia-forums.com/1g-1994-20...r-removal.html
Harry