Quote Originally Posted by ice15 View Post

Better tires (easiest upgrade)
Improve the way your car breathes. (Intake & Exhaust)
Lessen the weight (remove seats & spare tire, improve aero dynamics)
Improve brakes
Send it to a shop with proper dyno tuning
Upgrade the suspension
Upgrade engine
These do not come cheap so you have to consider how deep your pockets are. A set of grippy and sporty tires in 17" to 19" are around 30k (or more) nowadays plus lightweight rims of similar value, you are looking at around 50-60k. Brake, suspension, and engine mods would cost more than that.

If you want a quick and fast car for the price for the price of a Civic 1.8L, take a look at the Focus 1.5L Ecoboost. Since it already has a turbo engine (rated stock at 180PS/240Nm), a simple ECU mod will even push the power output higher.