James,

Does the car control the idle properly with the ISCV ??

To test this,

Put your foot on the brake in first gear and without touching the throttle, raise the clutch very very slowly to the biting point.
You should feel the engine apply more load to maintain the idle speed.

If that works ok, allow the car to idle once up to temperature and unplug the TPS and observe the idle CO for a few minutes.

If all seems ok, unplug 1 injector while running (anyone) for about 20 seconds then plug it back in and observe the CO over a period of about 2 minutes and see if it corrects.
(We are applying a disturbance in order to get the closed loop to work hard)

Otherwise, if all looks ok, your fuel pressure may be a bit high or you have a vacuum hose to regulator leak possibly.

The lambda sensor may be faulty but can only be tested with an osciloscope properly.