Anyone experience a water problem on the 2002 Subaru Impreza?
Water coming in on right side.
Front and back getting wet

We have seen the door seals (upper) leak on these a few times. The headliner will soak it up, migrating the water and subsequent stains forward and center on the headliner, thus appearing to be the windshield leaking. like most Subaru's the glass is the only contact for the upper door seal as there is no door structure there. I believe it is the same for the year you mentioned as well.

Another vehicle that does this on occasion is Pontiac Bonneville, the dw1105 years. As these get older the door seals shrink and release from the body, leaving large gaps especially on the upper side of the door opening near the 'B' pillar.

Sglass, does it have a luggage rack? I have seen luggage racks on these that will leak, and since the head lines is smooth on the back the water runs out the sides...

Sglass,

What did it turn out being wrong??

Yes, we have seen this before. It is a leak between the front doorglass and the body seal / gasket. It allows water to run into the car, looking like a windshield leak. Either adjust the doorglass, or replace the body seal.