Hank,
Everything I'm building is available commercially...you just can't buy it already built.
The only parts that are pre-fabricated are the circuit board and the extruded aluminum casing...everything else is just a big bag of 'lectronics. Some of the parts were hard to find but I was able to track down the super elusive motorola map sensor through some enthusiast groups.
The circuit board is not my design but is going to be customized to suit my purposes. I chose the circuit I did because it controls injectors, coils, and has 2 built in wide band O2 sensor controller (in addition to a ton of upgrade potential...egt, knock sensors, etc). I'd have made the board myself but some of it needed to be put together by a machine as many of the components are super tiny surface mount types.
As soon as I can get my engine rebuilt (still hunting for an inexpensive turbo and cams), I can install the ECU and start building a map...truly the part that I'm not looking forward to.
Dave