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Because those parts require engine management (EM)- especially on an 04+ due to the OL/CL fueling delay and other issues. Now, if you don't have EM, there's your problem. If you do, it may be that the tune is off.
The adjective "feline" applies to cats and related animals. The adjective catty (nasty) is used for people. There is no direct adjective for the noun cat. When a noun is used as an adjunct (cat whiskers, cat bed) or the word "cat-like" applies to things that suggest a cat, but are not cats.
Without proper tuning, there really isn't much you can do to break out more than like 15-20 horsepower (the obvious mods are lightweight pulleys, free-flowing exhausts, high flow intake, uppipe, cat-delete, etc.) To gain real power you will need to either buy a tuning program like the AccessPort, or learn to tune yourself with www.romraider.com. By tuning, you can teach your car how to actually work with the mods you installed, and you could very well gain more power from teaching your car how to use the installs you've done than you got by just physically changing things out in the first place. After that you get into the grounds of larger fuel pumps and modified injectors, larger turbos, changing engine internals, etc. Once you've gone that far you know far more than enough to need wiki lol