The injector flow rates are a constant that is relied upon for many of the engines running functions. Changing the injector flow rate until the afr is close is not the proper way, even though it gets the afr to where it needs to be in general.
You are supposed to set your injector values as per the gm data, then you correct your error via the maf/map.
If you don't do it this way and hack the injector flow rate tables, you end up with problems like this. The injector flow is a constant, what is not a constant, are the maf and ve values. If you are changing the injector flow rate to trick the engine into running richer, the computer is not seeing the proper air flow it should, and that messes up every table in the computer.
There are transient functions on ecms Who's sole purpose is to keep things like your problem from happening, they smooth out fuel shots and also timing transitions.
It makes absolutely zero sense to tune an engine via the injector flow rates beyond entering the proper base data. 20 percent fuel trim after building a new engine with a new air intake with a new cam, isnt even a lot, it is perfectly normal and always requires you build a new maf curve to correct it.
