alto 2010 model...78000 on odo.....ma alto gives me very very light jerk...gari kabhi kabhi jhatka maar k race pakarti hai.....recently tuning done tapping adjustment,platinum plugs installed,8mm wires installed,air filter changed, oil and oil filter changed havoline 10w-30,carbourator cleaned with 7cf carburator cleaner....before tuning no such problem....what could be the reason?