I think the problem is that the word "Tune" is used improperly 99.9% of the time on the forums here and most other forums.
I agree with dreamstang saying it should not need a "Tune" when the meaning of tune is used in the context of not needing a dyno, aftermarket chip, or aftermarket tuner tuning. The modifications should be well within the capabilities of the stock ECU to handle, which has been proved time and again by many others with similar or even more mods. You need to ensure that your engine timing and fuel pressure is set correctly.
I also agree with aegischief in saying it could use a "Tune" meaning a professional tune and using an aftermarket tuning aid and he is correct about the aftermarket MAF's tricking the ECU. Changing the parameters in the ECU to correspond with the injectors/MAF you are using is without a doubt better than just tricking the ECU. That should not be needed for your mod level, but it is the best way to do it.
Before I went to that expense I would tune it back to stock specifications in respect to the timing and fuel pressure. Your sputtering and backfiring is most likely due to one or the other, or possibly both being out of specs. Make sure your spout connector is good and plugged in properly too. I assume you removed it when setting your timing and then replaced it after you were finished?
Also make sure the vacuum line is connected to the fuel pressure regulator and does not have a hole in it somewhere along the line. To set the fuel pressure (if you have an adjustable regulator
), you start the engine and let it idle. Remove the vacuum line and plug it, set the pressure to 38-40 psi, re-install the vacuum line and you should be good to go.
You should not need a dyno, chip or tuner tune for a head change. The only time you really need a tune of that type is when you go with forced induction or nitrous
My 86 GT has been converted to MAF and has basically the same mods as you have listed and idles & runs perfectly with just a normal tune up.