Theres a few ways for under a buck. deffinatelly visit ebay and shop around. Cone intake filter replacing the airbox, $25 ~ 8hp + more torque and faster throttle. Bosche+4, $35 ~8hp + more torque. Adj. Fuel Pressure, $40 if used with more air and hotter plugs to burn more fuel, ~3hp @+3psi but a free flow exhaust is also helpful. Free flow muffler, $40 ~8hp + less torque and faster throttle and ricey sound. Ground Kit, $30 ~2hp + better throttle and accessories. If you dont just want to go straight, get some strut bars, and you can take turns faster. then if you want to spend more money, you can get even better power gains. Good Luck.
i sincerely hope ur kidding as with the rest of the replies to this thread...otherwise u need to do more research and stop listening to egay vendors...and btw...it aint all bout hp...by that i mean, research torque gains as well, not just 'more torque'...in response to the original guy w/ the question...prolly the best thing u can do is make urself a cold air intake...won't be as good as real cai, but better than stock...use the search button for more info...keep in mind u won't really get any real power from a civic for <100...u can get better handling w/ strut bars and sways (not tie bars, bad)...ur civic is light, and like they also said, making it lighter helps some...gl