OK....what am I doing wrong.In Heading Select mode I will dial in a heading, say 270 from 290, and it won/t quite make it to it. It will stop at 275 give or take a few degrees. Any ideas?

It's called "Track" vs. "Heading." The result of "winds."See this picture I just took as I am near to my top of decent into St. Louis this evening. I set the HDG to 078 and clicked on HDG SEL for a moment to illistrate this. Winds are 300 at 73 knots. My magnetic heading is 078 but the aircraft is tracking on airway J110 approaching the BUM VOR on a track of 083 magnetic. You can see the magenta dashed heading line on the EHSI lining up with the little white triangle at the top of the display. That triangle is showing you the aircraft "heading." The solid verticle line in the center of the display always shows the aircraft's "track" over the ground.