ok yes, the headers are the best exhaust Mod.
But if you just replace the headers and leave the rest of the system how its is, you will have slightly better peformance but not by much as the rest of the exhaust is restricting the increased flow. And the other 5 mufflers stop any decent v8 exhaust note.. so thats quite poinless to do first, wouldnt you want to hear the engine first by removing the mufflers???
I would say its best to remove the 5 mufflers FIRST, so you have the exhaust note and rid the restrictive mufflers. then replace with what ive said before. That would cost around $450 for parts plus labour. Thats not bad as you can get around 18kw power gain.
The headers made by rush imports cost like $650 or so which is quite expensive, ill do that eventually but its not that neccesary right away, they give you an extra 10kw or so at the wheels which is great and shows how restrictive they really are the stock headers.
But You dont need to rush in and do everything to the exhaust unless your prepared to spend well over 1100 all at once. once i have this soarer ill be pretty happy with the set up ive said previously, i do agree the headers are the most restrictive part of the exhaust but all together the 5 mufflers are much worse.
lol doing all is best of corse!!