Hard starting after a heat soak could mean flooding due to leaky injectors. If it's reluctant to start after a heat soak due to flooding, flooring the throttle should help.
Not sure why it starts easier with the throttle wide open when it's cold, unless the flooding is not clearing out overnight, which is possible.
Could be the problem is caused by your recent high temps or it could be something on the car. Take some resistance readings of the KE engine temperature sensor at cold and operating temp and see how they compare to spec.
Immediate start after a hot shutdown is consistent with flooding as the fuel from a leaking injector will take some time to build up and cause a flooded condition.