1500 bucks for a complete 104 engine is cheap! Youd have to pay about that for a decent used 103 series powerplant in this area!
MBRACER, I wouldn't worry too much about using the factory management stuff. Replacement parts are high and there were enough "quirks" with the factory stuff that make an aftermarket set up look real appealing. (stock wiring harnessess are notorious for spewing, as are oem mass air sensors,etc)
You might want to look into systems like ones from Haltech. Motec, Electromotive, SDS etc.
I am going to use an SDS system on my C36 motor and it is completely programmable, comes with a wiring harness, is very simple to install & set up, and I can eliminate the factory wiring, the oem mass air sensor, and am even going to eliminate the MBZ throttle body assembly & replace it with an aluminum adapter and a ford 5.0 liter TB. (the ford TB's are available in a wife variety of sizes and are no where near as expensive as the oem MBZ units,,,which also like to spew)
The SDS is a cheap and basic system, yet is capable of fast idle, cam timing control, closed loop etc if I want.
Since my car is a track only car, the only thing I am concerned with is HP,,,,therefore I am going to rent a dyno for a day to get my system totally "dialed in".
You don't have to do it with a dyno,,,,,,but I want to be able to actually "see" the results from my tuning & adjustments.
here is SDS website
http://www.sdsefi.com/index.html