From what I have been told, the walbro pump is good to 550 HP. If you're building more than that with the HP of the engine plus the desired amount of boost you need a larger pump to provide more fuel for both devices or a seperate pump just for the spray. That is what I am going to do next after replacing the the LSD unit. I want about a 2 gallon fuel cell and a inline fuel pump with it's own corvette fuel pressure regulated fuel filter feeding a consistant 58 lbs of fuel pressure to the nitrous kit fuel line. What happened to mine was I tried to make more HP than my fuel pump could keep up with. Definitely get a fuel pressure safety switch on that thing so that if you go under the desired pressure the nitrous will shut off. No need holing out another piston or burning the tips off the spark plugs because you're lean. Get the correct plugs, too. I had NGK TR6s when mine died but I still didn't have the FPSS or an RPM window switch installed. For what it's worth, one gallon of fuel is approximately 6" x 6" x 6" in volume if I remember correctly.

Don't forget to retard the timing back 2 degrees for every 50 shot of juice.