EXHAUST SYSTEM
You've increase breathing/intake, now its time to enhance exhaling/exhaust. You can't just take in without farting out(?)
What normal people would do is change to straight pipe and a bigger muffler for added sound, but no go. Yes straight pipe makes air exit faster, but where did it start?
Stock exhaust manifold is design with noise control and fuel economy in mind, hence not very good with performance.
Performance exhaust manifold is like a well connected highway(with no toll), with easing the jam(reduce backpressure) as its sole goal. In modern days, computers were involve in designing the manifold to ensure that the gasses will "join" or merge perfectly and exit quickly. Like F1's exhaust manifold(look below):
Because F1 engine eat(intake) as fast as it shit(exhaust), the exhaust system cannot afford to have any sound deadening stuff or catalyst to restrict airflow, hence the insanely loud noise and firework.
But your car is not F1. Anyway we're trying to keep it realistic. A simple 4-2-1 manifold plus straight pipe, plus high flow catalyst(you still need this to pass emmision tests), plus low restriction muffler(easier gas flow, and louder), is guaranteed to make your engine just a little more competitive than stock cars of same model.
If you're tight on cash, forgo the manifold, have the entire pipe starting from after the manifold, like this(look below), you'll still feel enhancement, namely the noise level.
"Stock pipe" vs. "High flow pipe system"
Decide well. Always remember:
MORE POWER = MORE FUEL CONSUMPTION
Theres no 2 way for this
