I have a 2004 Impala and every time it rains I get a flood inside the car. Pasenger side front and back and behind the driver but the driver carpet is dry. Has anyone had this problem and know where the leak is?

 

I don't know where your leak is. Somebody has to look for it.
Do you have a sunroof?

 

Water may be getting past the rubber water deflector located under the air inlet grille panel on the passenger side below the windshield. its where the cabin air filter is located. search for it on youtube, there are a few videos on this problem.
an easy way to tell if this is the problem is pulling back the carpet on the passenger side under the dash, then pour water over/around the cabin air intake grill and see if water is leaking there.

 

it’s a bad design. 2012 is like that leaks from every window. I can’t even leave the windows open a a half a inch and the water pours in..

 

get vent shades. AVS i found to be the best fitting. i had a set from amazon, and while they worked, the fitment wasnt right and the looked funny to me. i ordered the AVS brand and they fit and lined up very well.