Yeah... Freezing... Lol!
Modding for power isnt easy with normally aspirated (non turbo) cars.
Induction and exhaust are a good place to start, smoothes up the rev range and can give you as much (or as little) noise as you like.
Remap is another option, not best bang per buck but again, makes it a nicer ride.
Handling is another option for you, unless SA is like America, you will have corners in your roads, which means that wider wheels, lowered suspension a strut brace and better brakes may make you faster than any engine mods you can do for the same money.