91 Stealth TT has nasty misfire (I think)

Local Mechanics are clueless on this one.  This problem developed suddenly if that's a clue.  Start the car and the engine is misfiring at idle with no apparent (to me) rhythm.  When you try to maintain a steady speed the car bucks, sometimes violently.  But, if you floor it, it smooths out. I have replaced the plugs and plug wires.  I had the O2 sensor, EGR, and PCV checked. I even had the ThrottlePositionSensor replaced after the local dodge dealer told me it failed its test.  That did nothing but cost a lot of money. I'm looking for a solid mechanic referral in south central Oregon (I'm in Grants Pass) or some diagnostic guidance.  HELP!