My friend and I are going to tune it. We definetly want to use aftermarket in order to have better control and to manupulate everything on our own. It will bring more functionality in the way of ignition and injection. Thus, we are going to make sufficient changes and have a data of the performance.
Not trying to talk you into staying with the Motronic, but it can
do all that these days.
If you weren't turbocharging, then maybe I would try and convince you to try it
A wideband O2 sensor is essential. I quite like the 14point7.com
kits - but regardless of the brand, you really need one if you're tuning yourself.
This doesn't replace MAF/AFM etc, it just tells you what your AFR is. You then use that to adjust your fuelling.
Some EMSs incorporate "wideband logging" where you capture the AFR in the datastream. This will then show you what your actual AFR was at different areas of the fuel map, so you know which cells need to be leaner/richer and by how much.
Then there are some EMSs that can self-tune - with a WB connected to the ECU's input, it can adjust it's own fuel maps based on the AFR feedback.
As for AFM/MAF/MAP/Alpha-N, these are the different methods of determining air ingest (and therefor fuel requirements).
AFM (what you have on the standard engine) measures the flow of air with a spring loaded flap.
How far open the flap is tells the ECU how much air is being sucked in to the cylinders.
MAF measures the mass (weight) of the air entering the engine - well, actually it calculates rather than measures but anyway then the ECU uses that figure to calculate fuel.
MAP is Manifold Absolute Pressure, it measures the vacuum (or boost) pressure in the inlet manifold, which is then used with a VE (Volumetric Efficiency) table to determine the air being drawn into the engine.
Alpha-N is simple, it determines fuelling based on RPM and throttle position. Tuning an alpha-N system can be a long and tricky process though.
I'm no expert on this stuff, but off the top of my head some pros and cons are:
pro: you've already got one, and they adapt to engine changes well
con: they wear out with age, some say they obstruct the air flow too much and they take up lots of space
pro: reasonably fast to react, good at adapting to engine changes, good for fuel economy etc (so are used on most new cars these days)
con: still obstruct the airflow a bit
pro: cheap, don't obstruct the airflow at all, fast to react, small
con: VE table will need re-tuning on engine changes eg new cam/ported head etc.
pro: only need crank and throttle sensor, can work better than the others on ITBs or very lumpy cams, fast reaction time
con: not much fun to tune, needs re-tuning on engine changes.