How to increase your vehicle horsepower?

I have several questions regarding this topic. Here goes

1. What do you need to increase your vehicle horsepower? (I know there's the exhaust system, cold-air intake, manifold, turbo/supercharge) That all I know.

2. How much horsepower will it increase when you install all the stuff to increase your HP? Beside Nitro and Computer chip.

3. This question is regarding question number 2. How much HP will it increase the Honda Civic SI, Subaru BRZ, Toyota 86 (AKA Scion FRZ), all are around 205 HP stock and the last one I'm looking at is the Honda Civic Type R which is stock at 305 HP

Assuming you install twin turbo, after market or performance cold-air intake, manifold, and other stuff excluding the Nitro, and computer chip.
Added (1). Also, I like to know what is a good website to go to look up for all this stuff. I'm not a professional at auto stuff but I always like to drive one that tune-up. Another thing is where do I go to look up for car audio system?

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