is the 'Motor System Control Failure' fault light ON? in my experience, the ECU is pretty sensitive to irregularities, so a faulty with your hardware (sensors, etc) should trigger the fault light.
whilst trying to sort it out, some simple measures would include using some fuel injector cleaner with your next tank of petrol (may require a couple tanks' worth). the cleaner is primarily paraffin, so you can simply add ~150ml per tank via a small funnel.
also check for any cracks/leaks in the intake system, like in the plastic piping. because the problem goes when the engine is warm, it may suggest a leak, and heat expands the problem-area to seal it off.
lastly, do an ECU reset. the general process is:
*disconnect NEG battery terminal (at least 20~30min)
*reconnect; turn ignition key to MAR for just over a minute but do not start the engine
*turn ignition OFF and leave for just over another minute
*turn igntion to MAR and star the engine; do not touch the accelerate
*allow engine to run for 20~30min, idling; by this stage the cooling fans may kick in
*turn off, job done