E16SE lurching/jerking when feathering throttle

[Curtoise]

i have a problem on my car where it lurches about slightly when i feather the throttle to keep a constant speed, say normally when im on the motorway doing 65 and lightly pressing on the pedal it feels like someone is pushing the brakes on and off or like the engine holds back in pulses.....

it also happens in 30's and whenever i keep a constant speed or little throttle on!

i replaced and engine mount as i thought this might effect it but it still happens.

am i right in thinking it could be the coasting air valve mal-adjustment ?

[Curtoise]

anyone?

[nova_pipi]

it could possibly be air is being drawn in at the intake manifold, change the gasket and see this helps any, i think the coasting air valve mainly just effects the idle but im not to sure.