#1 all fuel systems that are not gravity feed , require pressured fuel to reach the fuel mixing device. The fuel supply requires pressure & volume . All systems have operating specs. for this . a. clogged fuel filters will cause a lowered fuel pressure / volume condition . b. fuel pressure / volume is critical for fuel injected powerplants . c on some fuel injected vehicles a 2 psi below specs will cause a no-start condition .
#2 the ecm does not (in this case ) know what the actual fuel pressure is. It assumes it is in operating range.
#3 I do not know if any factory sensors on the V11 are wide band O2 sensors or not .
#4 most fuel pressure regulators have this port that is open to atmosphere , connected to manifold vacuum . This will lower or raise fuel pressure to work with a change in throttle . I do not know why MG does not use this .
To emry , what is aDI unit ?