The Boy said it does "sod all"...
which means it does nothing!
(Where are you from? What language?)
My personal understanding with lightweight flywheels is that they are quicker to speed up (less mass to rotate) that regular flywheels. This should lead to increased acceleration. However, they are also quicker to decelerate, and leave your car with less momentum, which is not a good thing if you live in an area with lots of hills!
Having said that, I have never installed a lightweight flywheel on ANY car, let alone an Omega. And I'm certainly not as experienced on these cars as forum legends such as The Boy, and other people with 63 stars under their name!!!

Also I believe because the Omega has a different flywheel to normal, you would have to change the clutch too to match it. Prob quite useful if you're going to go anywhere above 30% of the original BHP.
From what I've read about tuning Omegas, good things to do are:
Fit fast road cams (not race cams, unless it's just a track car!)
Uprated clutch - depends how much you push it...
Remap ECU?
(Of course some things have knock-on effects, like needing more fuel = bigger injectors = different FPR = uprated fuel pump! etc) This is why most tuning is done in "stages", so things are upgraded simultaneously to complement each other.
The age old thing my friend say: Air in, Air out. This is a good place to start Mods, so Stainless Steel Exhaust etc. Probably more important than most of the other stuff I've mentioned!
It all depends what you want to get out of it!!! Most SERIOUS upgrades are probably over the top for a daily driver!!
One more thing though, is you can always loose weight! I've been told the Omega weighs around 1700 kg. So you can strip things you don't need, and even replace with lightweight (carbon fibre etc) but I think we're getting beyond the realm of what you're asking!! That's more for track cars and underground street racing!!!!
I hope some of this has helped, even if I have gone off on a bit of a Fast and Furious tangent!!
