Aftermarket exhaust sometime does not fit really well(mine is ARk Grip 2 burntip). you should/ must have a lift to make your life easier when it came to align fitment(some guy just jack up the car and do it- but it seem too dangerous and uncormfortable for me
)
in case it can not be align 100% perfect and you not happy with it, cutting and welding is a must. Bring it to a muffler shop. 100$ up to 150$ (involving cutting and welding) clean and professional.