Good response honestly. The TLDR is you can't go wrong with a BRFS, very easy to install, and it's not going to hurt the build by installing it, just make sure you log fuel pressure / afr / boost, and all the other tidbits to make sure the system is efficient & safe. Here's a little more in-depth response:
I remember when I used to browse the cobalt forums, a lot of people just went with stuff because it seemed right. Don't mistake what I'm saying here, I'm not applying that to you, just making the observation of those other folks. Your situation is you took a setup from someone and now you're refining it, and you're definitely looking to do the right thing either way.
I'm presuming you already monitor fuel pressure, and you correctly surmise changing the rail pressure will change the lb/hr flow of the injectors themselves. Most injectors are rated at 42-45psi, and many GM fuel rails are setup to run 45-60psi stock, and most of the pumps will accept up to 18v. I have no direct experience with the LSJ/LNF's yet, which is why I'm using general experience in my post. What you'll see some folks do is use a boost reference voltage booster, so they choose their injectors so that it's fine at idle, and increases voltage to boost rail pressure, to increase flow as necessary under WOT. Others set things up to bleed fuel off at low-rpm, which accomplishes the same, just in a different way.
If it were me, I'd do some math and run some analysis (logging pressure/fuel burn/afr/etc idle->redline->idle) and see if the injectors are well-matched for the application. I used to have a handy spreadsheet calculator somewhere with hundreds of real-life examples, and the ability to plug in your own data, but I can't find it right now (sadly). If I can find it, I'll post it up for folks.
If you're making 300 or more, I could see 60# being realistic.. the formula involved simply examines horsepower as a result of injector flow, cycle, and number of cylinders, along with a value known as BSFC (brake specific fuel consumption). If you have a map of your volumetric flow efficiency for the turbo/supercharger & engine, you can come up with your own tailored BSFC. FI for these motors puts BSFC at between .545-.6, from what my research tells me. A few folks claim the stock SC LSJ setup is .58.
I want to say the LSJ's came with 36# injectors, going on what I've heard. This also matches up with the basic injector math where a desired HP results in a necessary flow rate: (HP*BSFC)/(Injectors*Duty): 205*0.58/4*.85 = 34.9. So the stock 205 would need at least 35# injectors. This is based on my presumption of GM using an 85% duty cycle, which I've seen elsewhere. This is crank power of course.
Adding to this, I heard that GM used to sell stage kits for the LSJ, and they included 42# injectors. The first 2 would get you up to 240ish in power. The math shows a need for at least 41# of flow, which lines up with their stage kits. This is just going on what I could scrape online, for their former kits. In theory the math suggests that 42# would support up to 246hp, using the BSFC & DC from above. 60# would support 350hp. Without knowing the parasitic transmission loss, let me blindly presume 15%. So that puts a stock LSJ at 174whp, 42# at 209, and 60# at 298.
If you had a dyno map of the car that would really help. Do you know what your fuel pressure is from idle->WOT? What about your actual AFR & Boost? Stuff like that will help you determine where you need to be. If your duty cycle is 40% and you're still too ruch anywhere, I would definitely think injectors are too large, pressure is to high, or you don't have enough air volume going through the engine to use it all. Sometimes "turning up the boost" really is the answer haha. Seriously though, you're going in the right direction.
Sorry for the long post.. just thought I'd pass on some input. Let us know where you go, this thread could be useful to others.