I ran 18psi on a highflow on the factory ecu for years. As long as the AFM doesn't max out, then the ECU will keep running it properly. I was getting 4.95V on the AFM though
Generally that goes for most ECU's, if you don't max out the inputs, it will still present a stable output. The AFM is always the first to max, they always select bigger injectors from factory to 'outflow' the AFM.
The factory injectors are usually safe to 200rwkw as long as the pump is up to the task. The AFM is getting sketchy around 180rwkw