I drive a 2000 civic ex, and would like to add at least 20 hp without doing turbo or an engine swap... I was thinking about getting a 70mm throttle body, cai and an intake manifold... Then later on I would by headers if needed... Will this be worth it? Doing this also doesn't cost as much so its not a big deal... Any other recommendations would be appreciated...

 

go to a local muffler shop and get a full 2.5" exhaust system..
cost you about 170-200 ..

 

nitrous!! Get like a 50 shot since there rated at flywheel horsepower and that shall be what your looking for and a 70mm tb is way to big on a stock single cam

 

there are a butt load of factors that you have to take into consideration (motor, price, budget, etc) when trying to figure this stuff out. i think a 70mm TB is gonna be way to big for a stock motor with a CAI or SRI. your best bang for your buck is to get a SRI, better IM, quality header, and 2.5" exhaust. you will also be better off if you at least get a street tune to match the upgrades to the performance your looking for.

yea nitrous is a quick hp gain, but i would steer clear of it, as you WILL need to get your car tuned for nitrous and avoid pushing the button too much and blowing your motor.