Originally Posted by
blindsquirrel
You can't do two regulators like that. What's happening there is, the second regulator is forcing the rail-mounted regulator wide open all the time, since the one on the rail is trying to regulate at 51 PSI. If there is vacuum to the one on the rail, it's never going to reduce rail pressure when vacuum is high (low pressure) and raise it when vacuum is low (high pressure, = to atmosphere). Your second, non-referenced reg is the one in control since it has the higher set point, and you need to use injector data set up for a returnless/non-referenced system (copy tables from a '05-up L59).
Ditch the add-on reg and use the stock one on the rail by itself and you won't have to change any of the injector data in the file, since it's already configured for the L59 51 PSI referenced setup.