I discovered the noise is the nitrogen filled Brake Accumulator. According to Mitsubishi HQ it's a non-essential part that imposes no safety problems and only symptom is the chirping "urk urk urk urk" noise and MAYBE a firmer than usual pedal sometimes (but I've not noticed that yet).

It IS NOT a "recall" but only a warranty extension for 10 years or 100,000 miles, which ever is first.

So I'm glad. Anything that doesn't require a fix is welcomed!