Dodge Repair: Rough Running, P0305 code: 12 5.7L

Question
QUESTION: Hi, 2012 Ram 1500 4x4 5.7 Hemi 102 K miles.  Has had a slightly rough idle for many miles, maybe 20K. Dealers busy couldn't look at it. Finally at 100K started stalling only once in awhile while making turns or coming to stop sign. Then very rough running and 1st time code of p0305 misfire cyl 5.
I changed out coil and plugs and made sure to properly gap.
Smoothed it out alot but for just a short time. Blinking P0305 came back when I kicked down to passing gear, and idled very rough.
Changed plugs again just in case. Seems to have smoothed out some. Code didnt clear though when removing battery cables for 1/2 hour or so. Also MDS system stopped working as part of all this.
Any suggestions?
Jim

ANSWER: Please tell me what "MDS system" means?

---------- FOLLOW-UP ----------

QUESTION: Multi Displacement System, for fuel economy. At some predetermined point when engine is not under high load the economy of running on just 4 cylinders kicks in. The dash display reads "ECO" during that time. Now that is not coming on since I have had these problems

Answer
Thanks for that information, Jim. It may be that the MDS is purposely disconnected when there is a misfire.
The closest manual that I have is for '08. There are 13 possible causes listed for the 0305 code. Because the No. 5 cylinder seems to be persistently the issue I would set aside possible causes that are not pointed directly to that one cylinder. Aside from the spark plug and coil the items are:
injector no. 5
no. 5 injector control circuit
ignition coil no. 5 control circuit
ignition wire (to no. 5 spark plug)
I can copy the  specifics about the injector and coil and attach them to an email I will send to you directly. Let me know your email address but don't use @, instead use "at" or it will be erased from your follow-up question.
Roland