injector warranty - 2005 Expedition, any experience?

Should not be an issue at all. The service writer will confirm, through the VIN, that the vehicle is covered by that warranty. The service technician will confirm that your drivability issue is caused by the warrantied item. the correction is covered by the warranty.

You just have to hope the technician is skilled in diagnosing the problem. That is where choosing the best dealer's service department is critical.