One of the reasons I would have thought the headers would make a difference is because the stock exhaust manifold, if you look at it from the inside, it does not have a good flow of air off the back. Once the air exits out the head and goes into the header, it hits the back of the header and goes straight down. So I would assume if I had some nice headers that had a good flow to it from the get-go, I would have felt it would have made a difference. Hope I make sense. It's hard to explain the stock manifold, it's like an L-shape inside. You get me ? Thanks everybody for your comments, I appreciate it. This is my first Datsun and I'm going all out.