Hi Max23261.
Would help if you filled in your profile with your car details.
Searched your posts and you have a 2.0L CD (Don't know if it's
manual or auto).
Read this thread, and links in it, to ensure that your breather system
is clear and check your fault codes with the paperclip test.
http://www.omegaowners.com/forum/YaBB.pl?num=1193083316Check that your ICV gasket is in good condition and that your ICV
is still secure with no air leaks going into the mating faces where the
gasket fits. Your Inlet and Outlet slots in the throttle body, either
side of your Butterfly, are vertically aligned and the Inlet/Outlet holes
in your ICV are horizontally aligned. So you're twisting the airflow through
90 degrees. If your gasket is leaking internally or sucking in air from
externally, the ecu will have the devil's own job trying to control your
Idle speed via the ICV.
If all above OK, start looking for unmetered air via leaking Vac tubes.
3 on your Throttle body near the ICV, and the main Vac feed from lower down
on the intake manifold, that feeds your brake servo with tappings off that
to feed your HBV and climate control system.