Just curious about what the general consensus is on when it is time to upgrade fuel injectors. I have a LB9, so would the magic number be like 14s in the quarter? Or is there a more obvious sign for when they need to be upgraded? And to what extent do they need to be upgraded? Also, cost effective solutions are appreciated since my 4 year old absorbs most of my extra income.

 

You can get an adjustable fuel pressure regulator to artificially raise the flow rates of injectors but that's more or less a band-aid.
The only real way of knowing when you need to upgrade injectors is when your car is running lean enough that the ECM cannot richen it up enough (datalogging/scanning) to bring it back within safe parameters. A lean O2 code should set. Waiting for the code isn't exactly the best way of determining that your injectors are too small though.
Different fuel injector calculators all seem to give different fuel injector requirements. So take their suggestions how you will.