There is an increase in power over the later year models because the runners are rounded. The power would probably show on the dyno with some other mods like intake, tb, etc... I don't know if it would be noticeable while driving.
it is a noticable mod for power. just be careful who you purchase them from, because it may seem like a good price. but not much is ported....i've done a few and a lotta plastic can be pulled from the stock manifold because u need to use some epoxy from going through.
No... I don't have cams. I am going to wait to do that until the next round of mods. Currently I am putting on a Volant intake, Proflow MAF, more than likely Manifold, and the Eibach Dampers. The next round will likely consist of cams, cam gears, and head. I plan on going all motor with my car.