Give the guys a call at DIYAUTOTUNE.COM or MS3PRO.COM(same people) great service and the MS3 stuff is a good value.

I just fired mine up this weekend with sequential fuel and spark. I went the longer route and chose to assemble my ECU myself. It is an MS3X which has most of the features of the pro but lacks a few of them. The Tunerstudio program for Megasquirt stuff is easy to use, mine fired up and idled first hit of the key this weekend.

The MS stuff can do as much as you want it to really. Traction control, Dry or wet nitrous control, sequential fuel and spark, flex fuel etc.

The holley stuff is really cool but its not cheap. I no doubt have more labor in my setup but I saved lots and lots of money vs the Holley Dominator which is the closest feature wise to my MS3X.