I don't believe that the crank casing on the 1NZ would allow the fitment of any pulley much smaller than what we currently offer. I think 10% is pretty much going to be it!
Mine showed up last week from MicroImage. The car was with the Mrs. for the weekend so I didn't get to the install. Looks like it's gonna be another weekend before I can get together with a fellow Yarin and install the set. 10% underdrive FTW.... In the meantime I've put 'em on a chain and I'm wearin' 'em as "bling". I know my Yaris is gonna perform betta' with them than I am !!