Forget how much attention engineers pay to a car model's power-to-weight ratio, there's always some knucklehead around to stick a socket wrench in the handiwork. Take Lotus's Elise and its coupe sibling Exige, two of the most perfectly balanced road-and-track cars on the planet. Sure, the cars' perfectly sufficient horsepower can't snap a C1 vertebrae at the flick of a toe, but compromises must be made. Still, UK tuning shop Auto-Teknix had to go and stick an Audi 20-valve five-cylinder, turbocharged engine and six-speed gearbox in, just to see what would happen.
What happened was 300+ hp, zero to 60 in under four seconds (compared to 4.9 for the stock model) and a top speed of around 170 mph. Weight increased by 88 pounds, but they mounted the engine lower so weight distribution only changes by 2%. (Sure, tell that to the guys with the CAD-burned retnas, if they can hear over all the algorithms in their heads.) You can get your own, for around ten-thousand pounds.
Turbo Sled: More on Forcedfed's Tuner Elise [internal]