Displacement = torque. The ITR only has 1.8-litres of displacement and therefor has very little torque in comparison to say a 3.0-litre V6 or some domestic muscle. And it's true, on a launch the ITR is pretty slow compared to other cars with more torque, but she accelerates quickly and can catch up.

Utilizing high-compression and variable valve timing, the ITR engine keeps the intake and exhaust valves open longer than a standard engine, dumping massive amounts of air and fuel into the combustion chamber and thus making horsepower. Not fuel efficient at all, but that's how you make power from a small displacement engine.

The only way to up torque is to up displacement. That, or emulate it. And the only way to do that is with a turbocharger or supercharger.