Here are a couple tid bits I've learned over the years.
If wanting to "time" the injection event to occur while the int valve is open, it should start roughly around TDC exhaust which is 360° before TDC compression. TDC exhaust is where the intake valve starts to open. This is usually where I start and then tune from there.
It's usually not possible to completely deliver the required fuel to support a certain AFR under high load/rpm while the int valve is open. The amount of time that the int valve is actually open is something like 60% of total cycle time (depends on cam specs) and as we know it, many or most injectors are driven beyond 60% duty cycle unless running very high flowing injectors. This is why injection timing in high load/rpm states is kinda useless - because the injectors are open longer than the intake valve is.
Most OEM's size their injectors to go static at high load/rpm. I've tested tons of stock cars and all of them go beyond the 85% injector duty "danger zone" that everyone is so afraid of. They do this because it's much easier to get precise control for emissions on small injectors that have good control resolution. Injectors tend to act weird at low pulse widths (<1.5ms or so) and become non-linear and can actually deliver more fuel at smaller pulse widths. To combat this, the OE's size the injectors to run above 2ms or so at idle and be just big enough to provide enough fuel to support the engines rated power.
Tuning injection timing can net better off idle driveability and emissions but it doesn't mean squat for WOT performance. Most aftermarket engine management systems allow you to globally offset the injection start or end points and if you were to do so and do a bunch of WOT testing, you'd probably find that where the injection event occurs makes little difference on power output.
