Those kits use a FMU because its cheap and it will seem to work, for a while at least. It won't work well. Those companies either don't have the time or the commitment to produce their own piggyback/standalone EMS. Greddy's Emanage isn't bad but with all the necessary upgrades it's expensive, and I know Edelbrock's kit comes with some kind of piggyback but I don't know how good it is.

Uberdata or Crome are good, free alternatives to standalones like the AEM EMS, etc... Find someone in your area who can tune the car and knows these systems. Usually its just regular guys who know what they're doing from experience.