yea if your gonna get a header and catback exhaust
get them at the same time.
the header WILL help more if you get the exhaust with it...

although IMO the stock engine with free tuning mods could make more power than if you get all that stuff and dont tune it up

also i would recommend buying all new exhaust nuts from honda for each side of your cat, bout $10 shipped
here
illustration code #26

unless you get a high flow cat and it comes with the bolts

i would also personally get new header nuts
here
illustration code #9

since its a 99 you probably dont need to get the header nuts
but someone like me who is crazy probably would :yumyum: