sounds like you're being too stingy with your engine.
you probably wont listen to me for fear of going too hard on your .12SS, but leaning your high speed in small increments until you find that the car hums at WOT is a good idea to correct your bad idle. Low, inconsistant idle is derived from an engine with a bad high speed needle setting. Lean your HSN in 1/8th increments. Regardless of what the most experienced hobby shop technician tells you, an 8th of a turn is not overkill. You saying that the low end factory is not even 1/16th of a turn tells me something. The engine, especially the .12SS included with the RS43 Type-SS.. is not going to produce noticable results from 1/16th a turn.
Try to understand what gibberish i just splattered.