The symptoms are near enough the same as every other fuel pressure problem, so i'd suggest starting with the items that are cheap or free to check and go from there.
Fuel pressure regulator controls fuel pressure like an ecu-controlled bleed valve, as suggested by the name, very common fault and worth a look. The fuel rail pressure sensor is what detects fuel pressure, very rarely a problem, i've yet to see one fail and can only recall one or two instances where it was the cause of the issue - in those cases it was a wiring fault, rather than an issue with the sensor.
Putting the car back to it's standard map would temporarily conceal the problem, not fix it.
There's a lot of info in the link in my sig that may help you.
Fuel pressure regulator controls fuel pressure like an ecu-controlled bleed valve, as suggested by the name, very common fault and worth a look. The fuel rail pressure sensor is what detects fuel pressure, very rarely a problem, i've yet to see one fail and can only recall one or two instances where it was the cause of the issue - in those cases it was a wiring fault, rather than an issue with the sensor.
Putting the car back to it's standard map would temporarily conceal the problem, not fix it.
There's a lot of info in the link in my sig that may help you.