What screw am I turning the suggested 2.5 - 2.75 turns out as a starting point?
Bottom view of the TK carb, 2001 and newer TW's:
Different names for the same thing. I usually call it the idle mixture screw. It regulates the flow of fuel through the pilot jet (which is inside the carb).
My stock idle screw setting was 1 3/4 turns. Everyone's setting may be slightly different. I believe Qwerty has posted instructions on how to set the idle screw.