Mazda MPV smell

We have a 2002 Mazda MPV and it smells on the interior after starting and idling. It is kind of a gas smell or burnt oil smell. The mechanics cannot smell it always and have not found the source. IS this dangerous? They did a pressure test on the exhaust and itds tight.

Is the heat shield still on the catalytic converter? Is the floor pan still solid? I mention this because I had an odor in my 1978 Oldsmobile of someone ironing clothes inside the car. It turned out that the floor pan had rusted and the catalytic converter was heating up the carpet. I’ve heard of the carpet actually catching fire under these conditions. I would have the vehicle put on a lift and have the underside checked very thoroughly.