The trick is "Combination"!
You cannot place something by itself and hope to get 20 Horses. The Mustangs and Most V8 are by default "detuned" to meet legal standards, any mod would liberate hidden horses. 4 Cylinder cars are almost maxed out from the factory to keep up with the increased horsepower minimums. A bolt on item by itself doesn't guarantee instant satisfaction.
I was reading an article in "Sport Compact Car" about an exhaust for a Mini cooper. The exhaust actually reduced horsepower by 3 with the "Performance" mufflers the kit came with. With them removed, the car improved but the noise was unbearable. But because it is a low restriction and it was a Titanium kit, later mods would work better and horsepower gains will be more noticeable.
Again, $0.02
Ian
__________________
|