EFI + MAC-14 maxing ataround 5k RPM

[Ameer Antar]

You could actually be getting too much fuel. If that o2 reading is accurate,
12:1 is way too rich for no-load even at high rpm's. Too much fuel is just
as bad as too little in terms of power and proper combustion. It sounds like
you may have your fuel mappings dialed up too high if you're maxing out the
injectors. Pegging the injectors open is probably not too good for them.

42-lb injectors should easily get you over 300HP. Somehow I doubt you're
approaching that while revving it up. Try dialing the map down in steps and
see if that helps at all.