Suspension recommendation -
1. If you lower your car without stronger springs you will hate your car because it will bounce on the rubber bumpstops like some of the idiot honda kids.
2. If you add stronger springs without better shocks you will hate your car because it will bounce like a basketball. Example - some of the other idiot honda kids.
3. If you get the wrong stronger shock it will make the ride unnecessarily jittery and your tires will not maintain even contact with the ground. This will increase your chances of slides and spins in curves, turns, or under braking.
If you want to build your suspension cheaply by piecing it together it isn't very difficult and can be highly effective for both street and track performance. You just need to avoid buying the wrong item and then having to buy it twice. Used parts are often good deals, and kits often have incorrect parts for our cars. The spring rates will be incorrectly balanced between front and rear for our cars but perfect for a Civic. Or the high speed shock dampening will be perfect for a 66lb 18inch wheel/tire/brake rotor combo for a 350z but be horrible for a 38lb 15" Miata wheel/tire/rotor combo.
As for the factory manifold versus aftermarket header, there will be a negligible performance gain. 4hp is not worth $200+ dollars unless you are buying a lawnmower. There are plenty of guys who have gone turbo that would likely send you their good used manifolds for the price of shipping and handling.
Last edited by sixshooter; 05-18-2012 at 04:08 PM.