Take a look at the 9thgencorolla.com forum, and you will understand why the light weight is better then the underdrive, and also with the underdrive there is the issues with harmonic dampening unlike the Alutec one, since its a balanced one. Also the belt would be hard to come by too unless your ok with sourcing the belt from the US. I have also seen a copy of the dyno graph, on the 9thgen forum, the dyno was done on 1.6 vvti car cant remember which one, and there was a power gain, but i cant remember how much. I know i can get it done for $50 bucks let me tell you that coz my mates are mechanics, this job wouldnt take long anyways, guy from sydney we can do a group install. My friend also got hes done at a mechanic and they charge him $60 bucks for it, its a 30 min task. Cheers