95 Voyager runs rough

About 3 month ago, my Grand Voyager started running a bit rough. I changed plugs and such, but it just got worse. Took it in and was told it was the Coil Pack. I refused to pay $400 to fix it so I bought a new one for $50 and did it myself. Had to pay the diagnostic fee, but still was cheaper (The garage I took it to seemed to forget to plug the cooling fan backl in so it overheated and I had to replace a split hose, cheap, but it took forever to get to it).

Well, it ran fine for a while. Now, it is starting to run a little rough again. Honestly, I can't tell if the symptoms are the same as before or not. Some days are better than others. Luckily (I guess), the Check Engine light has come on. It does not stay on, and does not come on all the time. However, I was able to read the codes using the Ignition turn on and off 3 times method. 12, 32, 55. From what I can tell, this leads me to believe it's the EGR valve, or something related.

Not knowing anything about this, and not wanting to pay $130 for a new valve just to see if that fixes it, I would like some advice.

Any suggestions are appreciated. Thanks