[Turbo TA]

Nice build! The reason why you put the fuel pressure regulator reference line in the hat so that the fuel bowl pressure matches the FPR line. If you put it in the manifold, what happens is when you let off the throttle the FP will go to Zero psi due to the high vacuum in the FPR reference line. Also the carb is a restriction so there's a pressure difference from above and below the carb. You want to match the rise of the fuel pressure to the hat so that the regulator is more than the hat psi. Otherwise you will have issue with fuel flow and it will have a negative pressure. The fuel won't flow in an extreme condition.