I was under the impression that the quicker the motor revs, the quicker exhaust will exit and the turbo will spool up quicker resulting in less lag.
Please correct me if I am wrong, I really don't know much about forced induction. Thanks for your help.
There's a couple different things here that interact. I'm going to start by defining a few terms.
Boost threshold: The RPM where your turbo starts making boost.
Turbo lag: When you are at or above the boost threshold and abruptly stab the throttle, this is how long it takes for the turbo to spin up and make full boost.
Throttle response: An overall measure of how quickly the engine responds when you stab the throttle.
Turbo lag affects throttle response, but so do a lot of other factors. For example, poor fueling can result in a car that has very little true turbo lag, but the fuel takes longer to reach the ports than the boost. Result: A turbo that spools quickly, but a nose over bog even while the boost is coming up. A lightened flywheel would help if you tried to gas it while below the boost threshold, since the engine would benefit from help getting up to its boost threshold. So would lightening the car - or downshifting to the correct gear. A lighter flywheel would not spool it faster on a drag car if you launch it correctly. It might, however, help on a street car.
It depends on the situation. Overall, a drag car is not going to be hurt very much by turbo lag or bad throttle response, but a street car would be, and an autocross car would be killed by turbo lag.
