I was running a 15GPH with no problems at all and actually just upped it to a dual nozzle with the 15 and an additional 12- but I don't think it did anything other than use more meth lol. I may just go back to my single 15 since it was working well for me. be careful, I think they recommended a 6 or 7 gph for my setup- that is nothing for a boosted LS2!!
As long as your fuel is there, you won't have a problem at all. I just noticed the fact that you're an 04 too- kind of slow today haha- you should be fine. I have an 05 and am running 10 psi with a 15gph.