Whenever I parked my 122 nose down on a slope with a full tank, I had fuel vapors in the cabin. Upon tracing the source, I discovered fuel dripping out of the top of the tank at the sending unit area. It was a simple repair consisting of going down to the NAPA store and purchasing a new special fabricated gasket. I was surprised that they had the gasket in stock but the clerk said the sending unit was used on many foreign models and as a result the gasket with it special hole pattern was often called for. No more vapors.