318is flywheel weighs as much as a 325i flywheel(28.5 pounds). It's dual-mass seems to be a big problem since it kills first and second gear acceleration and this is also one reason why 318iSís 0-60 is so slow.
Some posts on BMW repair questions says you could try to use a 325i flywheel/clutch or buy an aluminum flywheel for your M42's clutch and an aluminum flywheel for using the 325i clutch.
Buying an aluminum flywheel for the M42 runs about $500-700 but is very light(requires no modification to be fitted).
M42 318is aluminum flywheels(12 pounds), and 325i aluminum fly's(8 pounds).
"The 325i flywheel requires a few other modifications to be fitted in the 318iS. Hereís what you need: 325i flywheel, 325i clutch, 325i pressure plate, 325i drive-pinion for the starter motor, and a Ď78-í83 323 throw-out bearing. Replace all these with the 318iS parts and it bolts right together. After all is said and done, your 318iS will have a LOT better acceleration in the first few gears, and deceleration will take place much quicker, which helps on the street and in the auto-x. Turner motorsport and a few other tuners also sell replacement aluminum flywheels for the 318is, but they also more expensive."