This happened to me as well, turns out the play was in the new pan hard bar end links and adjusters. Would up swapping my roto end link style bar back to just poly bushings. This time while adjusting on the car, I coated the threads with blue loctite.
Jack up you car by the frame , crawl under, try to move the pan hard bar left and right to listen for any sort of clicking or rattle..
2008 Metallic Alloy GT Convertible Premium
Show : black top| 18" bullitt polished wheels| CDC light bar and black billet replacement grilles | black/amber corner lights | GT500 rear spoiler| AH chin spoiler Go: FRPP CAI with StangHi tunes | Kooks LT's | FR500 axle back | Steeda Sport springs | Koni STR.t struts/shocks | J&M camber plates | UMI adj. panhard bar | LCA relocation brackets | GT500 LCA's | Hurst Billet shifter | 3.73 gear | FRPP axle girdle | Baer Rotors and Pads