Is that 378x9 or 425x8?
If the 378x9 as posted abve then yup nudge up the juice!
Your set-up looks half decent and I'm suprised your cooler is letting the chip get so hot. I think you could do with a little cable tidy session to help maximise your case airflow!
Good work with the case tidy, a 5°C drop (for free) is most welcome!
I'm wondering is OCCT showing you your PWM temps? If not then flick into the OCCT options and add the PWM if its not there already. Your board has a uGuru chip which shows all kinda of voltage and temp info so make sure OCCT is graphing that too!
if 3.4GHz (9x378) is passing multiple runs of OCCT then maybe switch it up to 3.4GHz (9x425) and see how you get on!