HDDP is right, I've been following this thread somewhat, so yesterday I done some searching on avarage HP gains when changing from a manifolds to headers. What I found was the average gain for adding headers is about 7 or 8 HP, most places claimed 7 to 20. But those were claims, one of the sites I visited they were doing a Nisssan I think they gained 7 HP. Besides spending a lot of money for little gains, you may be driving something that sounds like a ricer with a fart can. I can not say I wasn't interested at first, but after reading about actual gains and the thought of what it may sound like, NOT FOR ME.