As Tata Tiago isn't equipped with company fitted CNG and it is always recommended to get the CNG kit fitted from the authorised service centre so that you can avail the warranty services as well. If you get it installed from some other sources, then it may hamper your warranty. On the other hand, please make sure that the CNG kit that you are installing is RTO approved to avoid future troublesome. We suggest you to get in touch with the authorised service centre to know the exact costing and nitty-gritty of the fittings as they will be the best people to assist you in this concern. Check out authorised dealership details.