So here it is ...... i bought a new corolla a few months ago with the expectation that it would be having a good performance as compared to older converted Toyota's . After the car had traveled around 700 km i had got the car converted onto CNG . The kit installed was a simple Landi Renzo Kit and an advancer as well attached to it , with some other things as well . At first the car was really smooth and driving it intercity was excellent . However afterwards i took it to Lahore , very smooth , but then near gujar khan things changed and then the car had been knocking and then engine check indicator lit up , i did however manage to get it fixed ...... but still after every 500-600 km it needs to be tuned up manually or even earlier ........ therfore that day and the recent i still face the same problems .... could someone give me solution to this problem ? :S