[E92 420]

Ok so I keep getting this same list of codes come back after every drive. been happening for the last few months. car drives and pulls fine apart from a grumble i get when gently accelerating from low RPM it is a bad graunchy grumble sound very loud and causes vibrations. I originally thought this was the diff as I have a Quaife and solid diff bushings but iv had the diff taken apart by 2 different shops and inspected and both say the diff is in perfect condition. I don't get any warnings on dash or any limp modes etc... just this list when I read codes, and after searching I really cant seem to find much on them so Im hoping someone can help with what they are and what's causing them. they seem to be gearbox related?

CDAD (REQUIREMENT ROAD WHEEL TORQUE DRIVE LINE, BF)
CD99 (TORQUE REQUIREMENT EGS ELECTRONIC GEAR CONTROL, B5)
CDA1 (STEERING WHEEL ANGLE, C4)
CDA8 (STATUS KOMBI, 1B4)
CD9E (GEARBOX DATE 2, 1A2)
CD9D (GEAR DATA, BA)
CD98 (TORQUE REQUIREMENT DSC DYNAMIC STABILITY CONTROL, B6)
CD9C (SPEED, 1A0)
CDA5 (STATUS DSC DYNAMIC STABILITY CONTROL, 19E)
CD95 (OPERATION CRUISE CONTROL/ ACC ACTIVE CRUISE CONTROL,194)
CDA0 (TERMINAL STATE, 130)
2DC3 CONTROL CLAMP 15
CDB0 (DISPLAY GEAR DATA)

Im now leaning toward my gearbox being on the way out! mods are as follows
FBO with RB turbos, VTT inlets, RB hotside charge pipe alpina trans flash, and a custom wedge pump gas flash which is still being dialled in, its only on the 3rd revision.

[E92 420]

Anybody??