Got to read the rule a little closer to see what you can do. Mechanical injectors must stay but fuel pressure regulators are free. Nothing says the pressure regulator on a VW has to be mechanical. Vary the pressure with a servo in the place of a spring run by the ECU. Variable pressure at any rpm/load setting to a mechanical injector. Yes--it does work and can be done (at least on an old Porsche). Did I say how much I love the gray areas!!