With just the R550, but with the new OEM MAF and new muffler deletes, the car dyno’d 415whp. Given the 550 kit is true to it’s name, it should have 550chp.
Using simple math:
550/100 = 415/x
x = 75%, so 25% is lost in drivetrain.
Using similar math with the numbers after the tune:
415/550 = 462/x
x = 612.29chp after the tune.
With the new injectors I still need to get and install, after another retune, I should be making in the 490-500whp range. That equates to around 660chp.