header/ high flow cat Q

[81MALIBU81]

Do I need to use a high flow cat with a header? Would it be pointless to open exhaust (with header) into a restrictive oe cat? Do you guys running a header notice much of a gain? s14 ka

[murda-c]

Mine is very loud. shakes the car and stuff, but i have a 3" n1. not much faster without cams and tune...

[IStop4NoMan]

if you got the money, id say swap out the old cat for a high flow one. might as well free up the restrictive exhaust