that all makes sense now xulfiqar basically it all started when rpm is not getting stable and i feel vibration in engine or i can see engine is not calm the way it used to be , so i ask my cng mechanic and he said well
a) u have removed the tape which is now must in cng vehicles and the reference he gave is now company fitted cng cars are equipped with such rupper holes aswell like i had pasted a picture here .
b) he feels my tappets are jammed some how when i ask him how do u say that he said he needs to take the cover off and check it one by one to see if any of them are jammed or not , when i question him he explained it to me that he will basically note down and than he will put them back or if valves are damage he will change them , although i am not fully convinced so i have drop the idea to experience such experiment on my car .
last but not the least this all started with a vibrating engine so i dont know what would be the remedy or how to check it .
note : i have cultus 2001 so no rpm meter in that car he attached his rpm meter and told me rpm is not stable on cng , i feel no back fire , car pick is fine , milleage is poor but i feel the mechanic done a setting in that way that gas is consuming more as i feel like driving with power , starting is good so i guess the only problem is a vibrating engine and unstable rpm .