So, it goes lean at/or above 5600rpm? You obviously have better throttle restraint than I do. I'd kill mine within a couple days if I had to police my foot that close. LOL
One day,,,, and that day will come,,,,, when you accidentally push it to 5700 - redline. When you do and all conditions are just right,,, it'll pop a head gasket. All it takes is once. Lean is mean!
It may be years down the road, or not? But, when that happens, "and it will" you're gonna ask yourself: (Why oh why didn't I take the blue pill) and upgrade my fuel system?