SCT has a thing called Pro Racer Software which allows individuals to do their own tuning. Since my background is engineering (and I actually have patents on software systems among other things), I have the requisite skills to do my own tuning.
I had a 2003 manual FX4 that I put the RPCaster supercharger kit on and tuned that and it worked quite well except that the RPCaster intake was not all that great. The tuning was fine because all I needed to tune was the engine controls, and I had access to do all I needed there.
I had a 2009 automatic FX4 that I put the Moddbox supercharger kit on and that kit is very good. Tuning it was much more frustrating because SCT had not unlocked hardly any of the transmission controls, so I had no way to, for example, adjust the throttle setting to command the torque converter to unlock at a different point, or to command a downshift at a different point.
I did not change injectors for either of those because the factory injectors were plenty large for the boost I was running, especially considering that home is about 5600 feet elevation, and that I did not use the trucks for racing and they very rarely saw 5000+ rpm.
My current plan is to build a 331 to put in the 2001 that I have now, and that will be naturally aspirated and should be 350+ hp and 400+ torque, so that will need larger injectors - I already have a new set of SuperCoupe injectors that have plenty of capacity. The Pro Racer software will allow me to do all the adjustments that I need to make that work. I already have the unlock code to tune a 96 Explorer 5.0 pcm and have one of those for this project. I have already used it because I built a 351 Cleveland and put it in the 1966 F100 I have, and used some adapter plates from Price Motorsport to mount the Explorer intake on that and tuned a 1996 Explorer pcm to run the Cleveland (which takes significantly different timing table etc. from a Windsor). SCT has unlocked a lot more controls on the Explorer pcm than they have on the Ranger pcm, so doing what I need on the Explorer pcm has not been an issue.
Tuning an engine yourself is not for the faint of heart, and not for someone who is not logical and methodical. It helps a great deal if you have experience with PID control loops from somewhere, so that you have a good 30,000' understanding of how it all works together. Then it is a matter of carefully adjusting what you believe needs changed, one thing at a time and carefully testing and data-logging to see if what you expected to change actually changed and what the effect was. There is a lot of tweak and test and repeat, especially when you are highly motivated to not blow something up....