Hello, I hope you are well.
My name is***** will see if I can help you.
What access to diagnostics equipment do you have?
If you are able, allow the vehicle to cool overnight, in the morning connect the diagnostics and view the live data from the engine sensors, look at the temperature sensor readings, ideally all should be within a couple of degrees of each other, especially the engine coolant temperature sensor, all should be close to ambient temperature.
If the sensor is faulty and reading low temperatures, the engine would start and run normally then get worse as it warms up as it would effectively still be on choke.
Another parameter to view on the live data, is whether the engine control is in closed loop when the problems arise or open loop still.
When the engine is first started, the ecu runs in open loop, essentially ignoring various emissions sensors during the warm up then switches to closed loop as various parameters are met and thing like the heated oxygen sensor in the exhaust come up to operating temperature.
I question if it is sensors that either report the temperature of come into closed loop as the vehicle warms up that are reporting incorrectly, as such this would not log a fault code like a broken sensor would as the ecu would not be able to recognise the sensor is lying.
This would also explain the good running when cold, given you have already paid attention to the ignition and timing system.
Another area I would be looking at is the injector quantity adjustment figures, and considering whether an injector has a fault as it is warming up.
Unfortunately, it appears I can not have a discussion without it giving the option of rating as this question has previously been attended to, please take into account that I have not had the opportunity of conversation as yet.