The fuel pressure regulator internal diaphram may have a hole in it
allowing fuel to leak into the vacuum line that connects it to the
intake. Any decent shop should know to check this. Unplug that vacuum
line from the pressure regulator and check for the presence of any fuel.
There should be NONE. Plug the end of the hose and see if it helps the
running on a brief test basis. In any case the fuel pressure should be
also be checked. These regulators are getting to the end of their lives
as many on this list have experienced.

Mark