A lightflywheel definetly helps your performance. You will rev faster too! What brand of flywheel did you go with? I have the findanza flywheel. It kicks ass and you should be proud of having a lighter flywheel as some only wish they could afford one. Be happy, put it on. If you have racing pulley like I do to, you definetly will rev faster and your TT will move!
Your friend who's comment "it does pretty much shit for the car" dont know jack.