Greetings Yovan, I'll offer up my thoughts but understand I hold no credential in Ford 6.0's. Bear with me as you may have already done these steps. Before spending money I would confirm what your current injector electrical side status is.
1) I would obtain access to a diagnostic monitor like a Scanguage, Forscan, or AutoEnginuity.
2) Confirm both starting batteries are the same brand, age and 12.6-12.7 volts resting. Use multimeter.
3) With ignition on waiting for glow plugs observe voltage drop from glow plug demand. It is common to see voltage drop to 10-11 volts due to demand but if its 8 volts or less replace batteries. Indicated on scan tool.
4) Confirm alternator is supplying mid 14 volts at normal idle and is stable indicated on scan tool.
5) Confirm FICM voltage is 48 volts and rock stable at all rpm and driving conditions. Indicated on scan tool.
If all that checks out your performance issues are probably not your FICM or injectors. At that point I would upgrade the FICM as a reliability improvement for the future but not expect any performance cures. And, move on what the other issues are that are causing the issues your describing.
My only recommendations for FICM reliability improvements (only after confirming steps 1-4 from above are satisfied) are either Ed at FICMrepair.com who offers the lifetime warranty option OR the Bulletproof Diesel power supply with the 6 phase power supply for redundency.
Regarding the 53 or 58 volt options. It is my understanding that the higher voltage FICMs was from the high horsepower builds that were running higher and sustained HEUI oil pressures, think dyno rigs and sled pulling. Then it was believed by regular truck owners as a solution to prevent injector spool valves from sticking (sticktion). Sticking spool valves can not be prevented or cured by increased voltage in my opinion, that is an oil issue in the spool valve. I don't think it's just hype to run the higher voltage but 95% of all 6.0's aren't modified in a way that would need the higher voltage.
2005 SMB RB 4x4 6.0 PSD
A rocket on the pad is safe,
but it's not what rockets are built for.