Well do realize that a car will loose power over time and mileage. You might want to look into more of a complete tune up. Try wires, cap and rotor. Run some fuel system cleaner.
I was running the Platinum +4´s I didn´t notice a difference unless I drove down to sea level, but what will make a difference is how much spark there is. Try a better coil. Try advancing your timing a couple degrees.
Try making the intake piping start big then get smaller to the size of the throttlebody. Remember when the piping gets smaller the air "speeds up." Could effectivally create a ram-air system. I had great experiance using a K&N filter, I say stick with it.
Go with exhaust. Get rid of all the extra weight in the car. Rip out things like "Intake mufflers, " stuff you just dont need. Make sure you´re getting good traction, check your tires. Try replacing your tranny fluid. Make sure your wheel bearings aren´t moving like they´re chunky. New fuel filter is always good.