Pick problem of Vitz do not start until the car has reached 50,000/km or more..mostly catalytic converters choke at that time, because the fuel available in Pakistan is of bad quality mostly mixed with other least quality fuels, this makes it choke!!..
my car is pretty new so it does not have such issues and mileage is less than 25000 Kms...however to be on the safe side I removed catalytic converter, and added a middle "Doholki" to get rid from the noisy engine sound which mostly happens after the removal of catalytic converter.
As the result the pick is very good and, equal to new Gli and adding of another "Doholki" made engine smooth and sound-less.
other issue is of fuel, 3 cylinder cars use Hi-octane (mostly 92), here in Pakistan i believe it is not available and it is of poor quality, so people mostly add super and hi-octane, i use super+hi-octane is 50/50 ratio, sometimes in 60/40 ratio from reputable pumps, in Islamabad (from PSO diplomatic enclave and Caltex Super Market)...I do not recommend using hi-octane alone for 2008 and up model, because it has less octane numbers which are required..