My G60 has had no mods.
Since I've bought it I've had an issue with the "CAT" warning light coming on almost instantly.
I've got time this weekend and plan on having an old buddy help me diagnose.
The timing belt, spark plugs, cap, rotor and wires were replaced 30000kms ago and nothing changed.
Car was getting 6L/100kms leisurely drives - 9.5L/100kms pushing it, so seems good.
Just replaced the charger with a Stage II-III one (while I save to rebuild it with BBM) keeping the pulley and chip unchanged.
Before replacing plugs, cap, rotor and wires I hoped to address what this could be.

Should I remove the ISV and clean/soak?
If so, what's the best way?
Some say to do an ISV delete, but I prefer to keep everything stock.
Still appreciate your remarks...
I do still have original charcoal filter and hoses running (have had some recommend removing this)

Buddy has a timing light so also want to check and verify the timing is correct.
Appreciate response on the best way to do this.
Either in your own words or opinion on the best link to use for neither him or I have ever done so on a G60.

Thanks in advance for your help