With a guage conected to the end of the pipe it reads 2.1 bar so does this mean it can achieve a good pressure but not actually testing the demand of the system. (flow requiremetns)

How i look at it is (probably wrong) testing with it t'eed into the sytem is going to measure pressure under demand so then a flow is created and if the pump can't keep up with demand then i'd assume pressure would drop off rapidly.

Or it may have a leak.

Is my thinking correct?