Sounds like if you can get it around 10, than this test is over! It would seem the pressure regulator and return line are fine.
To completely rule out the regulator as a factor, there are a few other items you could try. A leaky vac line to the regulator, or a leaking diaphragm in the regulator itself would give a false low signal, increasing fuel pressure to the rail when it isn't needed (And resulting in the BLM drop as the computer attempts to compensate).
If you have a hand-held vacuum (Mity-vac) pump, you can test the regulators ability to hold a vacuum... Just hook the vac line up to the regulator, pump it to pull 15inHg or so, and see if it is a slow or quick drop to 0 (Or if you can pull a vacuum at all!). Adding a T fitting to the vac line will let you use the gage on the pump to measure the vacuum the regulator sees when the car is idling. Both these tests should prove the pressure regulator system is OK and you can look elswhere.
To completely rule out the regulator as a factor, there are a few other items you could try. A leaky vac line to the regulator, or a leaking diaphragm in the regulator itself would give a false low signal, increasing fuel pressure to the rail when it isn't needed (And resulting in the BLM drop as the computer attempts to compensate).
If you have a hand-held vacuum (Mity-vac) pump, you can test the regulators ability to hold a vacuum... Just hook the vac line up to the regulator, pump it to pull 15inHg or so, and see if it is a slow or quick drop to 0 (Or if you can pull a vacuum at all!). Adding a T fitting to the vac line will let you use the gage on the pump to measure the vacuum the regulator sees when the car is idling. Both these tests should prove the pressure regulator system is OK and you can look elswhere.
