Is the tactrix/mazdaedit user friendly?
Not really, unfortunately. If you are familiar with tuning, its not that bad on the surface. But once you start digging in and finding out that some of the maps are improperly labeled and sometimes completely backwards, it can get frustrating. My high det timing map is actually open loop timing. My low det timing map is closed loop. High det fuel is open loop fuel. there are several instances like that and its different for each ROM ID.
Do keep in mind that the purchase of the software and cable is part of the e-tune from most tuners. Some have an option to rent the stuff, but if you ever have the desire to do it yourself or just monitor it, get the package. You can also go straight to Epifan to get it.
I wouldnt go with a smaller intake pipe ID. If its not the same physical sensor, it may not even fit. Im fairly certain that my MS CAI is the same ID as stock. The gains are from the non ribbed intake tube, cone filter, and better flow characteristics after the filter.
Note: My experience below applies to the 1st gen, but Im sure its the same on 2nd gen. Hell most of the concepts are exactly the same as how my Evo ecu was done.
There are several groups of long term fuel trims. You said you saw -4. That is likely only for the maf flow that you were measuring at that time. For example, 0-35hz may be the 1st "zone" that has its own stored LTFT. Then 35-60hz would be the next. And so on. That way its not applying the same correction across the board.
Commanded AFR doesnt tell you a whole lot more than what the map is calling for. LTFT, MAF Scaling and other stuff impact Actual AFR. My Actual AFR was below 10.0 AFR on the stock tune.
I use a bluetooth adapter and Dash Command to monitor stuff on the fly without my laptop in the car. They have a Mazda PID patch that opens up knock retard and some different ways to log afr and other stuff. Im suprised that scangauge doesnt have an actual afr loggable item. But now that I think about it, I may be using the custom Actual AFR PID. You may have to log Lambda instead. Lambda of 1=14.65ish AFR for gasoline.