Dave, here is some reading, something you'll need, there are others out there, I have heard others that have use them and are happy with them.
I run Speed Density (MAP) on my Hemi, On '87 Mustang, '91 Corvette setup, I don't like the looks of the MAS valve, the only differenxce between Speed and MAS is the duration on the cam, Speed needs vacuum, in stead of air flow.

---> http://www.bgsoflex.com/megasquirt.html


Pat