Hi there I had the same problem with my car a few years ago. After some arm twisting at the dealership I got them to preform the PCM - Low Vehicle Performance TSB 18-013-02 created 04/22/02 This should be all that it needs. It has some thing to do with the way the pcm reads the rpm. It takes about 20 mins for the dealer to flash and install the updated software for your car.
Make sure that you only have the computer flashed by the dealer. Many independent shops have bad ROMs. I had my 2004 Neon flashed during a routine visit to the shop that I've been taking my older cars ('77 Mustang, '86 Camaro, '68 Corvair) to for years. Rough idle problem showed up the next day. Had the dealer flash it and everything went back to normal. I asked my indi shop what the deal was and he said that Dodge often doesn't release the proper ROMs outside of the family. Same goes for computerized alignment specs and such.
Had same problem with rough idle and check engine light codes for random cylinder misfire. After replacing plugs, wires and coil pack, turns out the only problem was that the spark plugs were not gapped properly! Re-gapped plugs and runs better than ever now! Easy fix for me. Try checking this before wasting alot of $$$!!!