MSD MAP Sensor readings

Sounds like you're getting close to having a good tune. I have a feeling mine is going end up being in the carb tune. I'm getting an air/fuel ratio gauge put in so I can tune off of that.
Average absolute pressure at sea level should be 14.7 and the higher you get the lower your absolute pressure will be, plus barometric pressure will also change that, so it sounds like your MAP is reading correctly. I found a chart that showed manifold absolute pressure vs vacuum Hg. 14.7 MAP equals 0 Hg vacuum. 7.0 MAP equals 13Hg vacuum, thats about where mine is at. Your MAP is reading 4 to 4.5 which means you are pulling about 16 Hg which should be about right because a stock cam will create more vacuum.