Just found this in Zoom No.19

"on most normally aspirated engines the difference between idle pressure of around 35psi to full load is in the range of 7psi. This slight rise theoretically increases the delivery capability of the injectors as the load increases which as an end result gives the manufacturer the ability to write a much flatter fuel delivery curve in their software - or indeed use a smaller than normally possible fuel injectors.
What most folks don't understand though, is that the factory atmo fuel pressure regulator is equally at home on a turbocharged engine due to its inbuilt rising rate setting."

"in all instances I have seen, there is enough range left in the atmospheric regulator to cope with an additional 10-15psi of boost supplied by a turbo charger.."

"...don't be fooled by having to lash out great amounts of money on a special turbo fuel pressure regulator unless you can see by watching a pressure guage that your unit does not respond"

I hope I haven't breeched any copy right laws!!!