Rover owners: jiggle valve missing

to day i removed my img as i was sure it was leaking into the inlet ports. symptoms were white smoke on start up and a slight misfire and loss of coolant. i had checked for leaks and could not find any, there was no signs of overheating phew. these symptoms disappeared when the engine was running .

when the manifold was off noticed that some one had removed the jiggle valve from the manifold.

but a new viton gasket on and everthing is running fine.

my question is why did they remove the jiggle valve and will it cause any long term problems.

i did notice that the head gasket had failed in the past as i had to clean the expansion tank out but the coolant was fine just remains of gunk stuck to the side.