Hi
Just to add the more I look at the info for the GM 12561462 injectors the more convinced I am that the LS6 engines did indeed have a 28.8 lbs/hr @ 58 PSI injectors from say '01 - '03. Then maybe from '04 onwards when Holden were carrying on the LS1 in the Monaro's they used an uprated injector from Bosch but with the same GM part number on them (mine have that number on them). Here's some flow data from an LS6 injector (931) with an LS1 (890) injector for comparison. Dated from '05 but the injectors were from a second hand pullout motor in the US.
Also to back this up if you look at the Holden IFR in post #6 ignoring the somewhat odd shape of the slope, the injector values go up to 4.6 g/s which is 14% above the LS6 injectors.
Attachment 14959