It was the 57th FG (P-47s), see reports for June 9 here:
64th Squadron report:
http://www.57thfightergroup.org/oper...64_3_jun44.pdf
"On our second mission (of the day), we bombed a destroyed(sic) (should be destroyer) in Porto Ferraio harbor. A direct hit was scored resulting with a blinding flash and a column of white smoke rolling to a height of 500 feet. Two more of our bombs scraped the side of the ship and it is believed that this enemy vessel is badly damaged."
65th Squadron Report:
http://www.57thfightergroup.org/oper...65_5_jun44.pdf
"The third flight led by Lt Thomas dive-bombed and strafed a small destroyer spotted by Lt Andrus. Results a smoking, listing destroyer caused by three close hits on the starboard side."
The first attack may have been all 12 planes in the 64th squadron. (It is just not clear from the report.) The second attack appears to have been just four planes (of the twelve flying in the 65th squadron).
The 57th FG was part of the 87th Fighter Wing (57th, 79th and 86th FGs) which, in turn, was part of the XXII Tactical Air Command.