hmmmmm ??? weird !! ......i have installed cng both in my Vitz and Altis....with accumalators and advancers and all that shit......but mines working PERFECTLY fine !! .....
Your mechanics are not probably educated enough to handle VVtis.....because this thing happened with my vitz once....i went t install mufler and that fool cut of my downpipe switch !! As a result the car would should check light and on signals it would turn off !!
Later i found a gud mechanic and got it fixed.....Try findin sum educated and well known mechanic in Lahore.....thats the solution !