isn,t the fuel line just a unrestricted flow back to the fuel tank after the regulator as its only a drain off pipe for the extra fuel released by the regulator. There is a valve/solenoid thing which is connected to the regulator by a vacuum hose. Which in turn is connected to the inlet manifold via a vacuum hose. This valve/solenoid is also connected to the
ECU.
Could this be connected wrongly??