I might add to Scott's list  intake leaks' clean nozzles venting properly ,whats your MAP at idle ,your rpm increase at ICO with a slooow pull , doe's it idle ok when cold and rough when hot.

Gene,

 

You are right, especially the intake leaks.  It is easy to develop a leak at the rubber sleeves that connect the intake runners at the sump.  A cocked tube, a crack in the rubber or a loose clamp.  That was one of the first problems I had with my engine.

 

I wonder if the Lycoming site has a trouble shooting check list?  By golly, it does.......