Interesting. I'm sure it gives us another ceiling that many of us didn't know about
. On the Mazdaspeed platform, we could upgrade our HPFP internals (larger piston/cylinder to push more fuel). I remember buying my internals from KMD Tuning...they were VW pump internals LOL. The pumps, and even just the internals, were expensive due to the tolerances required during manufacturing to avoid failure. Our VW pump prices don't look too bad though.
The good news is that Meltedsolid didn't upgrade his pump, so I wouldn't think it would be necessary to fuel an IS20 upgrade with a reasonable max boost pressure (~20 PSI). An IS20 @20 PSI vs IS12 @18 PSI will be a nice difference in flow. The IS20 will still be well within the sweet spot of the turbo's efficiency whilst the IS12 will be already starting to run out of breath.