Well my stockies were 190's and I switched to Ford brown tops which were 370's and it was fine. Up to 9 psi
ECU did ok with them and idles awesome.
Then I went with DSM 450's and they were ok and it idles fine up to like 11-13 psi.
Now I am at 580's SRT-4 Stage I injectors and they are ok.
My ECU seems to compensate to whatever I throw at it.

Now here is the problem 450's were rated at stock DSM 43 psi of fuel pressure so if we do the math my is 50 psi on idle stock fuel pressure.
You take new fuel pressure-50 and divide it by old fuel pressure-43, you get 1.162, you take the square root of it you get 1.078. You multiply that to 44 because DSM injectors are 44 lbs or 450 cc and my formula works for standard LBS and you get 47.44 which is lbs per hour, and you multuply that to 10.5 to get the cc, and you get 498 cc injectors.
So just because I ran the 450's on 50 psi of fuel pressure opposed to 43 I was idling 500cc injectors and it was fine.

Now going to SRT injectors I thought I was upgrading but it was minimal because SRT's use stock 58 psi of fuel pressure.
So if you do the math they come up to 545-550's on idle, and the ECU has no problem pulling and compensating right now.

So if I run 650's which are rated for 43 psi of fuel, I will be trying to idle 707cc injectors since I run 50 psi of fuel pressure on idle so I think that my ECU will be able to do it.
That is also the reason I am asking people NOT to try to offer me anything bigger because 650's are already 710's, and 780's would be over 900.

That is about it. Under my measurements 650's at 70 psi of fuel pressure would be something in the range of 880's and they would support about 18-19 psi hopefully.