Thermiq room2 – 303/304 and 307/308 already taken in my Diplomat from 2014

I’ve just took ownership of a house with a 2014 Thermia Diplomat. Not sure the exact model possibly Diplomat Optimum G2/G3
When trying to connect the room sensor and EVT I’ve noticed that the ’standard pins 303/4 307/8’ are already taken and connected to a larger 8 pin cable that goes inside the pump housing. There is no Thermia room thermostat installed on the pump.
There is no mention of the pinout diagram in the installation manual or on the pump housing.
Any ideas as where I should connect the 4 cables to have the full functionality? Disconnect/solder onto the existing 303/4 and 307/8 or try the free ones 327-338?
Picture of the board : https://imgur.com/a/Ock4gMI

Thanks in advance!