I read in Don from FBO's tuning guide that the regulator needs to be real close to the carb to recieve a good signal of fuel pressure so it'll respond fast and keep the pressure steady. I haven't tried it either way so I don't have any experience on how much difference it makes.
I'm running a Carter high flow mechanical pump and it only developes 6.5 psi max so I don't run a regulator. Mines the street pump. There is a strip pump that puts out about 8 psi that needs a regulator so it don't push the needles off the seats. What does yours max out at? If it's no more than 7 your fine without one.