After hours of checking the O.R. and following events on maps from the period. My final opinion was there were only two Whitworth Artillery pieces under the command of Pemberton from late 1862 until the surrender of Vicksburg in July of 1863.
A letter by General Taylor to General Pemberton dated November 10, 1863 mentions the two (2) Whitworth guns now at Vicksburg.
One Whitworth gun (2.71 inch) was under the command of Col. Ed Higgins in command of the Water Batteries near the City Center and Higgins left. It was used against the boats around the canal cut. Between May 24-26, 1863 it was moved to the rear and placed in the lines just behind Moore's Brigade. It is shown on the list of guns on the rear lines dated June 18, 1863 and on the list of guns surrendered by Moore's Brigade, Forney's Division in July of 1863.
One Whitworth gun (3 inch) was under the command of several Brigades and manned for a time by a detachment of the Pointe Coupee (Louisiana) Artillery at Fort Pemberton. It is mentioned during the engagement of March 13, 1863 against Union boats. It is mentioned again with the Point Coupee Artillery Detachment at Fort Pemberton on April 7, 1863. As the water level fell at Fort Pemberton in late April the guns were removed to Snyder's Bluff. On May 1, 1863. Sherman mentioned bolts being fired from the hills near Snyder's Bluff. The gun is mentioned again as being abandoned at Snyder's Bluff on May 17th but this report was corrected by General Hebert and he mentions the gun was brought to the trenches on May 18th and placed in the lines with Baldwins Brigade, Smith's Division and placed under his command, under the direction of Captain J. L. Wofford, Co. D, 1st Mississippi Light Artillery. This gun burst on that day and is shown in the report of guns lost and destroyed under Smith's Division.
No other Whitworth's are mentioned anywhere in Mississippi during this time period.