06 Mustang GT (CAI-Catless H pipes) All that is known

Purchased a 06 GT recently and the lineage of the vehicle died with the seller's brother. Really have no idea what he "did" to it and the idea of possible having had the diff tinkered with and maybe a tune... IDK.. rides like (Moderated) so I'm ripping out the rear end. I have a Diablo I3 Platimun for my other truck and have purchased the Ford License. My question is regarding the "stock...

Tuner knowledge requested