HP limit with 1-5/8 headers

Will they afect the power in a negative way? To some extent, yes. Will you notice it? I seriously doubt it. It takes a lot of sorting out to get to the point where swapping to custom or longer or larger tube/collector will make a feelable difference. Does it make a difference, defiantely..But on a street car, you wont notice it much. At t he track, you can feel ET changes in the .10s, but a street car on the street, it's hard to notice a change of .5, unless you're racing a consistent car and you can gage against it.