Originally Posted by wstar

That's a whole other argument, which has been debated at length elsewhere on this and every other car forum on the planet, largely inconclusively. Given the evidence at hand for our cars, I'd say whether dropping one in is a good idea really depends on your situation. As a general guideline: if you have plans to go Forced Induction it's probably best to not mess with the pulley (SC pulley size needs adjusting, and SC/TC both are adding a lot of stress and doubt to the harmonics arguments, and at that power range the benefits get even more marginal), and if you want your mods to be easily removable it's probably best to not mess with the pulley either (the Al ones slowly weld onto the crankshaft). Enough of them have been (correctly installed) on NA engines for plenty of hard miles without incident though. If they were causing any serious mechanical balancing issues, we'd have seen destroyed crankshaft bearings by now.