[CorneliusRox]

Well, with marine injectors, you can't run as high of timing (at least until ~3000+ rpm) because you're shooting way outside the bowl. I bet switching to any similar sized 145deg spray pattern is going to give you much better street manors. I'd do 145deg spray 7x11 or 7x12 injectors, and a better set of delivery valves. Then start messing with the AFC spring and tuning. I bet you'll be really happy with the setup.
I'd leave timing at 21-23deg as well.