Did you change to bigger injectors? I just have the factory lq9 ones and I'm sure they'll be maxing out the duty cycle with the cam.
Should I go with the 8.1 injectors or bigger?
No. Mine's a FlexFuel, so the injectors already have headroom. I forget the details, but I wanna say they're safe for 600HP. Don't take that as the gospel, though.
Just figure for 100HP over stock and see if FF injectors would support that for yours. You can get OEM injectors for relatively cheap. They have a couple different sizes (mostly height variances), but should be able to get some that fit where your stock ones were. You likely will have to get connectors and pigtails, too. Or adapter harnesses.