I've read a post on the Focus forums of a guy who had a aluminum flywheel who went slower in the 1/4 than with the stock flywheel. Lighter flywheel sounds good, but in accelleration, the heavier flywheel may take a bit longer to spin up, but when it's spun up it uses it's heavier mass to help keep it moving and you'll accelerate faster than with a lighter flywheel. It's all in the momentum, a heavier flywheel has more.

2000 Rio Red I4 Cougar 200whp & 210wtq at 9psi 254whp & 276wtq with NX 35shot WRX TD04 Turbo, Cut Short Shifter, Strut Tower Bar, 17" ZN Wheels, Roush Springs, Starion Intercooler, NX 35 shot, HKS SS BOV, Full 3" exhaust,StreetFlight Chip