You shouldn't have to upgrade the pump, not unless you are way over 600 hp. I did the Walbro upgrade, it is not easy, especially if you have a RT10. Just watch your a/f. You will probably run out of N2O volume before fuel. Most of the single line/solenoid dual sprayers can't go more then a full 200 rw without hitting the N2O restriction.
If you want to go more than 200 rw you will need a dual stage setup with more than one sprayer. If gas is the fuel it has to be in a dual sprayer (N2O and fuel tied together) to allow the N2O to atomize the fuel. If you talk to NOS they will tell you the best flowing sprayer has a max rating of 240 hp, however, that is flywheel and with everything else perfect. Remember most of these sprayers are for direct port application and you are typically spraying 8 of them
