Yes fitted pas from mgf along with the stalks, the stalks are a real challenge as the internal circuit does not adapt well to the Sierra wiring, it can be done but I would not recommend it.
Fitting the pas was straight forward you need a signal from the engine and road speed, both signals are only to activate the system.
Both signals can be generated using a pair of NE555 Adjustable Module Duty Cycle Pulse Frequency Square Wave Signal Generator
The mgf system regulates the power assistance from a torque sensor built into the steering column.
I would recommend a switch to turn it off if not required.
I changed my XE a few years ago to a modified Z20LET
Let me know if you need any more Info let me know