Weird problem help please
 

Here goes it first start a long time ago. When I almost ran out of gas and it was raining heavy. The car has the bottom tray mod ( not my me). It start spitting and spudding like it had no gas after I pit gas in it. When I got home the air filter was wet. And when I leave it for a while it doesnt do it. What is the reason for this to happen. Like maf sensor or o2 stimluator please help. And it goes away if u run the car for about 5-10 minute it will smooth it