[E.pocock]

I am designing an Intake manifold for my university's Formula Student Team and have encountered a problem with mass flow convergence at the end of the runners. The image below shows my issue, the solver seems to give a realistic result (the mass flow rates should be near equal) after the first 50 or so iterations but then it fluctuates randomly and gives bizarre results.

I have an equal pressure drop between the 4 outlets and the inlet and am using a pressure based K-e turbulence model.

Any help would be much appreciated.

Mass Flow Convergence:

Geometry: