Now, I do not yet know if that holds for all ME7.9.10 versions, so far I only looked at the Abarth and family program code, perhaps the weak 120 hp version of the code have this done differently. Will see with time, to be continued...
So I continued. So far there is nothing in the Abarth code that would make me believe that there is any program limit to work with boost pressures above 2560hPa. The mentioned 120hp / non-Abarth code (in an ECU that actually sits in my car) is a different story. It is surely 5120hPa ready, but things are purposely capped. In particular, the end of the procedure that calculated pvds_max limit for the target boost pressure says:
flash_085A70:[F2,F6,4E,A5] mov r6, xram2_word_0F254E
flash_085A74:[7C,16] shr r6, #1
flash_085A76:[E0,07] mov r7, #0x0
flash_085A78:[00,86] add r8, r6
flash_085A7A:[10,97] addc r9, r7
flash_085A7C:[F0,68] mov r6, r8
flash_085A7E:[F0,C9] mov r12, r9
flash_085A80:[26,F6,FF,7F] sub r6, #0x7FFF
flash_085A84:[38,C0] subc r12, #0
flash_085A86:[FD,03] jmpr cc_ULE, loc_085A8E
loc_085A88:
flash_085A88:[E6,F6,FF,7F] mov r6, #0x7FFF
flash_085A8C:[0D,01] jmpr cc_UC, loc_085A90
loc_085A8E:
flash_085A8E:[F0,68] mov r6, r8
loc_085A90:
flash_085A90:[5C,16] shl r6, #1
flash_085A92:[D7,40,3D,00] extp #0x3D, #1
flash_085A96:[F6,F6,64,07] mov xram2_word_0F4764, r6
flash_085A9A:[7C,16] shr r6, #1
flash_085A9C:[D7,40,3D,00] extp #0x3D, #1
flash_085AA0:[F6,F6,68,07] mov pvds_max_0F4768, r6
flash_085AA4:[98,60] mov r6, [r0+]
flash_085AA6:[98,70] mov r7, [r0+]
flash_085AA8:[98,80] mov r8, [r0+]
flash_085AAA:[98,90] mov r9, [r0+]
flash_085AAC:[DB,00] rets
0F254E is one of the pbrints, F4764 is a low range (2560 hPa) target boost pressure limiter, but this one is not used anywhere. pvds_max is the full range capable (5160 hPa) limiter that is used, but as you can see from this code, it is purposely cut down to 2560hPa. This is easily fixable by changing 7FFF to FFFF and shifting the assignments and bit-shifts a bit, and from further looking into the code this should do the trick.
For pvds that is. Because I found this, now the load calculation based on the intake pressure has to analysed to see if similar stupidity has been introduced somewhere there (with the hope that even if it had, a fix would be equally simple). To be continued again...