UPDATE: I replaced the thermostat and Expansion tank Lid..
The solution now doesn't boil over (50/50 mix), but the rad fan isn't kicking in at all, even when left to run for 30 minutes...
Hopefully, its because it doesn't need to, but I'll have to give it a good run out, see if the Rad Fan kicks in or the car overheats.
And did it? :)
I ask as I’m having the very same issue... I’ve now changed the stat, the CTS and the wiring mod tonit the expansion bottle cap and checked that the fan does come on when the plug is removed from the CTS (indicating that the ECU is operating correctly in terms of grounding out the relay properly?) and yet the blooming thing boils up on me with no movement on the temp gauge. I’ve also checked for 5v at the pink/green wire and the resistance at cold was 3020 and when I ran it up for a while roughly 300 iirc