Do i have to cut off the stock cat back so the stainless headers can fit?
i'm ordering them + the SLP Loud mouth ASAP,
i'm so worried about the shiping cost i guess its ganna be like $3000 or more for SLP heads/cam and other parts
No, the stock cat back is it's own unit that bolts up to a flange. From there forward if you put headers on will be altered. But the new setup should be able to bolt right up to that flange on the cat-back.