Originally Posted by black_jack

You must be careful fitting a very light flywheel - you may have to set the idle higher (eg 2k) to get it to tick over, it may make the car SLOWER off the line because it bogs down when you let the clutch out, and the car may slow down uphills (more than with a stock flywheel)

A lightweight flywheel will not "fix" problems with turbo-lag, best to get to the route of the problem itself

A light flywheel works better on a lightweight car (race car) the heavier the car, the heavier the flywheel needs to be

A 2wd is fine on a 4wd -an ultra light flywheel may cause problems and/ or make the car slower overall than with a heavier flywheel