TD5 mis-firing and surging (i think)
I think one of the key points is that after disconnecting/wriggling the looms the problem was worse, then better.
Check the loom particularly where the injector harness leaves the main loom down towards the steering box and across the front of the motor.
Note also that all sensors can be disconnected from a TD5 without causing your symptoms.
The only sensor to cause an issue is the CPS. Usually because the loom has been subject to leaking FPR and become brittle.
And FYI my post you quoted was definitively the upgrade Chip/Map.