||by clamping the ends which was inconclusive (not confident in the clamps sometimes it held, sometimes not so much). Next I pulled the plenum and fuel rail to test with paper towels wrapped around the injectors. No leaks (multiple times).
The only thing I can think of is a injector has a slight leak somehow when opening, but I'm not sure how to test that, or if it is even possible. My fuel pressure when idling is normal.
But yes, my symptoms seem to fit leaky injector. These were new Nismo 740cc injectors from SZ and they now have a grand total of ~50 miles on them.