You can install the cutouts on a stock exhaust system . You don't need headers . You will need to leave the cats in place or your check engine light will come on . The placement of the cutouts , I'm not sure of . It would kinda be a waste putting the cutouts after the cat , it would defeat the purpose but again I'm not sure if it would turn on your check engine light on if it were before the cat . I know we have a guy on here (Chefred) that has his cutout installed before the cat , but he may have his O2 sensors turned off . That was capable of being done with some old programming on older tuners . You can always post up this question oin the forum and see what everyone else has to say . I'd tell ya to pm Chefred but you're not eligible to do that yet . Post up your question and he'll probably respond to it . Talk to ya soon . Tom