not sure on the size of the hole, but there are lots of people on here getting 600+HP at the rear with Don's injectors
example 01 4x4
stock HP 180 hp @ the wheel
fueling/timing + 120 hp @ the wheel
mach 6's 200hp @ the wheel
turbo(s) 80hp @ the wheel
these #'s are approx at the rear, but you can see his 200hp injectors
will give you a close # to the RWHP
hope this helps a little
Scott