Turbo lag is the delay between when you press the throttle and the turbocharger starts producing boost pressure. Since a turbocharger is an exhaust driven compressor, the engine must be producing a sufficient quantity of exhaust gases to drive the turbocharger, which may only occur once the engine gets to a high rpm. Ways to reduce turbo lag are to lighten the turbocharger components to reduce inertia, use a smaller turbocharger, or use a blowoff valve to reduce turbo lag after shifting.
