X300 rough running when warm

I have 97 x300 3.2 and it runs fine when cold, but as soon as the engine warms up it runs rough and very rich. I have changed the coil packs and spark plugs, new air filter and cleaned the throttle body and butterfly to ensure it all runs free with no sticking. All to no avail, any ideas on what to try next?

Oxygen sensors.

Not sure if you have two or four.

Thanks,worth a try, I will try and track them down and have a look and if necessary replace.

Been suggested that the problem could be with the engine control Unit - if I do change it, does the ignition key need to be reprogrammed?

Runs fine when cold seems to indicate that the car is fine in closed loop. Once it starts reading sensors for fueling, things go awry.

Try the oxygen sensors first. They are sensors that do need to be replaced after so many miles. Yours are probably original to the car.

The ignition control unit (whatever that is) is not something that would change when the car is warm or cold.

AFAIR no the locking etc. is down to the security module.
It helps to know where you are located as there are many regional variations!