Pontiac Repair: Pontiac Grand Am Water problem and other, pontiac grand am, water problem

Question
I have a 1995 Grand Am 3.1L V6, and there is a lot of water getting into it, maybe an inch deep if it rains a lot. The water is not coming in the weather stripping because we replaced and sealed all that, and there is no water on the doors or sides. It's almost like it just comes up out of the floor, but we inspected the floor on the outside, and it's fine. Just curious where this water could be coming in. (It's not an engine problem because it only does happen when it rains)

Also, sometimes the car shudders, even jerks pretty violently when accelerating. I've had it for a year, and it did not do this for the first 3 months, so I'd like to know what caused it, and how to fix it.  

Answer
I believe you have a leaking windshield. The majority of GM's well into the 90's had a problem with the primer they used on the pinch weld area. This is the small area of metal that the windshield is glued to. The primer didn't protect properly and rust would start to form and then water will get in behind the window and from there the only place it has to go is in the car. You can test this theory by using a garden hose on your car and only running water along the window and then watch inside to see how long and where the water appears. As for the second part there are too many possibilities without more info and probably a test drive so all I can say for this is to find someone reputable. Hope this helps and good luck :)