The Toohighpsi kit works in conjunction with the DI setup. You will probably need to upgrade your low side fuel system as well to supply the added fuel needed from the tank side to the high/rail side depepending on your power goals.
It is similar to how GM did the C7 ZR1. Same LT4 high side parts (I’m currently using) with an added Port Injection setup.
My low side is good for 1300hp. I’m running a cam with a +32% fuel lobe so it overdrives the high side pump too. Still limited to about 850whp without supplemental port or the Lingenfelter pump and XDI +30-65% DI injectors. That is a 6-7k proposition for parts alone. Meth is an option but I don’t want to rely on it for additional fueling and have a $200 pump failure take out my built short block.
Coyote fuel system upgrade: Injectors and pumps.
LT fuel system upgrade: