N55 e82 issues

[Aminal135]

Hi all am wondering if anyone has experienced what I have .
Have recently done lots to my N55 valve cover thermostat water pump HPFP
Car has had all major things done . I find it sometimes blows black/grey smoke
And sometimes has a flat spot wot
What I have had is on wot all the dash lights came on limp mode and wipers came on as well . Has new battery alternator charges 14.2v but mhd shows 11.7 volts .
Car has fmic charge pipe cat less Dp and exhaust stage 2+ mhd
I’ve heard the power cable behind the glove box can be a problem for
Factory being loose

[Windy5000]

That doesn't sound good, hopefully someone here will be able to help.