2003 Sonata Base I4.

After sitting overnight the engine starts quickly, and goes to high idle as normal. After a few seconds drops RPMs and it begins to stumble, picks up RPMs and then stumbles a second time, as if it is starved for fuel.

Shortly after it smooths out and drives well until parked overnight.

While troubleshooting a previous hesitation problem which turned out to be a vacuum leak, I replaced the following over a couple of months;

1. Fuel Pressure regulator
2. Fuel injectors (all)
3. Throttle position sensor
4. MAP Sensor
5. MAF Sensor
6. Fuel Pump

There are no codes, the car drives well around town and on the highway.