this is were every one is wrong. wieght reduction does increase hp. ripping out your seats will not affect dyno numbers, but a lightwieght flyweel will "free" hp.
lightwieght flyweels do not make hp. what they do is free hp. so that this is clear your flyweel reduces hp like your transmission does. lighter flyweel = less hp lost, not hp made. this is a diffrent kind of wieght reduction that shows on the dyno.
If you read what I said once more, you'd realize the word I used was GAIN which means to get something you did not have before. Before you install a lighter flywheel, you have less wheel horsepower. After installing the lighter flywheel, you GAIN wheel horsepower that you did not have before. The HP was there the whole time at the crank, but you did not have it at the wheels. I never stated nor implied that flywheels generate HP. Once again, this is all semantics that could easily be ascertained with an ounce of common sense.