What's your favorite mod you've done for under $250?

Gas bonnet struts.

Under 250$ hmm.. New used car i guess :D

Light weight flywheel.

Cup holders 30 GBP

I bought Porsche brakes

“I support globing warming’ sticker

Clean my lacquered up throttle body and readjust the throttle cable.

http://www.spoonsports.eu/spoon-products/honda-civic-eg6/52385-ek9-000.html

CT stickers, 50+ bhp every time!!

Spray Plasti-Dip my wheels