VE plays into the the PR required for the amount of flow. That takes into account all the turbine wheel restrictions, etc. I'd say that it's been proven that ~17 psi is around 420 whp with the right octane. Falls right into line, right in the region of maximum flow for given PR.
Also, the rpm this compressor needs to make a nice amount of boost is lower than I expected for it's size. These things can be pushed way beyond the 310-320 whp that the flash tuners keep harping on as the max of the hardware. I'd say that is absolutely not the case with the data presented.
'15 AW/SO F80 M3 6MT: IND cosmetic package, Gloss black grill surrounds, Macht schnell 15mm spacers all around, 3M crystalline
'07 997 TT 6MT, Arctic Silver/Sea Blue: FBO, stock turbos: 5.9 60-130 E85, 997 platform record