Toyota Corolla XLI (old model 2007). I have installed CNG kit (Landi Renzo) for the last 02 years. For the last one month I am experiencing problem when I switch from CNG to petrol. While in run accelerator does not respond for quite a while then engine regain power as petrol has now reached in the injectors. It was not so initially. What could be the problem. I have change fuel filter but problem remains there. While shifting from petrol to CNG there is no delay to gain power.