Its the cheapest way to improve your power to weight ratio. instead of paying for ECU or engine work, making the car lighter is cheapest way to go. Plus, how far do you go? some cars have rear seats removed, Matt's Clio TT is stripped apart from driver's seat and dashboard! The cup is 89Kgs lighter than 172/182 but isn't that much better, as they've had to replace the heavier parts with lighter equivalents...if you wanna be extreme, you'll have to remove carpets, soundproofing, doorcards, seats...leaving nothing in there that doesn't control the car!