The above mentioned rubbish will do nothing more than wasting
your time and $$. Other "performance parts" do work, however they
ususlly come with tradeoffs.
For example, changing to harder shocks and lowering your car do
improve your handling somewat. But at the expense of comfort.
Choose your "performance parts" carefully. Cos some do give you -ve
performance gains.. such as putting a 3" exhaust system on your
1000cc car. other than ego boosting sound effects.. your car is
likely to be slower than a stock car! Of coz, most ppl will not
notice that.. coz with that kinda sound effect.. you car "feels"
really "fast and furious"! 
Same goes for open pod air-intake that sucks in hot
air under your bonnet.. whahahaa!!
