There is no boost referencing the factory fuel system or regulator.
The factory fuel pressure settting is ~52psi. At 12 psi boost, the effective/relative/differential fuel pressure is about 40psi. There is 40psi more fuel pressure than there is intake manifold pressure, assuming no pressure drop in the system.
40psi with 650cc injectors isnt exactly a ton of fuel. If the pressure is dropping in the system, its even less. To resolve a case of pressure drop might extend the 650s into your required output. But if there is currently little-to-no drop occurring, than you just need larger injectors.
To investigate the minimalist remedy for your car, you would need to acquire some data. Is fuel pressure dropping below 52psi at the fuel pump module? This means the fuel pump is out of steam. Is fuel pressure holding steady at the pump module, but falling at the rails? This means you need upgraded plumbing or a return system. Is fuel pressure holding everywhere but the injector duty cycle is topped off? This means you just need injectors.
Most often, customers rather spend their money upgrading all of it in one shot rather than investing in detailed diagnostics to precisely locate the problem.
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