Another thing while I remember, I'm considering one of these:
http://www.megasquirtpnp.com
Looks to be one of the most straight forward ways into megasquirt and it's all laid out for the m20 requiring only a few minor changes to get the engine running on the base map.
I was looking at the millermaf / WAR chip which looked interesting and has some good feedback, as well as a few negative ones online. What I like is that it's simple, what I don't like is that it seems like a very closed system.
I might start with a wide band lambda sensor and AFR gauge to get an idea of how the engine is running. I know is rich on idle and lower down the rev range but I don't know what it's like furhter up. In theory the standard 2.5 injectors are getting close to their limit with the 2.8.