Change to AGPR 12PP8 plugs first, or IK27, these will give a std ignition system it's best chance.
Hunting isn't caused by a iscv, as said iscv only raises rpm above base idle, check your fuel pressure, make sure the fuel filter is not more than 18 months old, then fit a new CTS and set the co to 2.5%, or whatever the chip maker says.
The main thing that raises the idle speed is the TEMPERATURE of the engine talking through the CTS to the ecu and this telling the iscv to open a bit more, it could just be a very low base idle and a sticky iscv giving the trouble, but the cts and fuel filter should really be service items, mine are changed every 2 years, most are not.
tabetha