Well, I'd say it's most likely not the race plug - hooked up to the outlet and cranked rail pressure up to 25k for 15 or so seconds and didn't seem to be so much as a drop coming from the end of the fuel rail. Lift pumps also power up and seem to be operating, although I don't have a gauge to verify pressure at the engine.
If I had some mechanical issue causing it, wouldn't that show up in the form of a missed target such as vane position, boost, fuel pressure, etc? Interestingly, on the 450 tune, fuel pressure drops off initially, but then catches up and maintains desired for the remainder of the time...
