That's one of the nest things about Megasquirt. They've developed an open source app called megatune that will read the WBO2 & correct maps automatically. You can also log just bout any sensor you'd like to. Most importantly, they have experts that will help out on their forums. I know the M20 has run successfully on MS, and I've heard of a few running turbo M42s. You might be able to get a map pretty close right off the board.
Tuning is very expensive here. Dyno time is like $50 & up/hour. A decent tune would go for 4-5 hours, I'd figure. That'll pay for the whole MS deal right there.
TunerPro is a great package too, just depends on which way you'd like to go with it. OEM Bosch stuff is pretty well built too, not a bad idea to go that way. I'd start with stock maps & get a TechEdge or JAW WBO2 to log your mixture, then tune from there.