It'll depend on how much fuel pressure you're able to provide and how well your specific injectors handle those pressures before locking up.
My old boosted combo saw 317 HP (roughly) RWHP on 19 lb injectors with roughly 90 psi on the fuel gauge (FMU, of course). I still had some room to go given that the AFR (indicated by wideband) still showed me a bit on the rich side (indicating that the injectors had not topped out yet).
If we use a conservative figure for drive-train loss (say 10%) then I was supporting 348 fly-wheel-horsepower with those stocker 19 lb injectors without issues. Granted, the injectors were probably putting out a pretty crappy spray pattern, but they were able to support the load.
Though I seemed to have been lucky, I've spoken directly to other folks that have had injectors lock up (fail to pulse) at these kinds of pressures. Just be mindful that the potential for something like this to happen, does exist.
