CNG in City 2008 IDSi

I bought 2nd hand city idsi 2008 couple of months back and went to CNG Complex for conversion to CNG. Following is my exp there and with the car:

Had Landiranzo kit with Landi Adv and Emu for 40k. Guys did a clean Kit installation but use no protection to avoid any body scrach. Electrical work was also fine and had hot water connections too. Due to CNG load sheding on Sat here in rwp had to travel for CNG fill.

On return car started well on CNG and every thing looked fine till next morning when I started the car. It kept dipping rpm on idling. seem like it is missing a power stroke. Also it does miss on 1700rpm exactly. Can not drive at all on CNG at start. Next morning tried again and had same issue. After running couple of kM on petrol, switched back to CNG and it started running fine but after 5min got check Engine light

Went back to CNG complex and surprisingly the guy said that it is normal and you will get this light because of oxygen sensor in exaust. If you want to fix the problem will have to install another emulator for it and will cost 3500 additional.
This problem was never informed before installation and now got stuck with Check light and RPM issue (only when engine is cold works fine after 3-4km on petrol)

my car has done only 29000km and should not be a problem with accelerator body or anything else.

Check light solution is understandable but should have been told before starting installation.

RPM issue can be because of faulty installation of Adv.

Car runs fine on petrol.

Just wanted to share my experience and may be some advise too.