I am currently running 24lb injectors in my ride... I have my fuel pressure set to 40psi. I find that it runs the best at that pressure. I have ran it as low as 30 and as high as 45. If you have a fuel pressure gauge, look at it when you rev it up... where ever it reads at, set your idle to that number.... (that's what I did to get an idea of where it needs to be) Then I got her dynoed and made the propper adjustments from there.
I can't help you out on your MAF... I have a Pro-M and I just plugged it in, and ran

No clue about the voltage.