The last I heard Carquest synthetic was being blended by Warren Oil Co. in Dunn, NC. Carquest is still a Raleigh, NC company until the AAP merger finalizes.
I made some phone calls today and confirmed that all Carquest brand full synthetic oils are still blended by Warren Unilube at its West Memphis, AR plant. Apparently Warren uses that plant because it has more capacity than its Dunn, NC plant.