The stock rail is fine from a power standpoint. Although, on E85, I've had others tell me the coating in the stock rail flakes off and causes problems. I've yet to see this happen on my car, however, and I inspect the rail often.
The stock FPR is holding you back because you don't have a way of knowing or regulating your fuel pressure, which typically leads to an inconsistent tune. An AFPR is one of those basic building block kind of mods, IMO. It's not one I'd ever skip out on, especially considering how cheap they are.