Andy I had a similar problem but on my Rover V8 Mog.
False, silly pressure reading on the dash gauge.
The problem was with the sender unit to the gauge. My car has two senders, the other is to the ecu so it will shut down the engine if there is a pressure problem. I replace the gauge sensor and problem solved.
The rover shows 4 bar on cold start, runs when warm at just under 4 bar, dropping to 1-1.5 bar on idle. This low idle pressure is worrying until you realise it is normal!
I don’t know how the roadster measures pressure...is it just a single sensor or two like the Rover ?
