water leaking inside thru cowl grate

There's a collar around the cowls fresh air openings so water has to pond in there a good inch or more deep before flowing over the collar and into the vent boxes. Then the vent boxes have 2 different type gaskets that could fail letting some of that water bleed between underside of cowl and vent boxes. That is unless there's a lot of rust through. The cowls drain openings are at each end so what goes out there runs down behind the dogleg end of the front fenders. A space between 2 bolts under that with whatever spacers were needed to get panel alignment are supposed to let the water and debris out to the ground. So if you do have a lot of leaves, pine needles, etc.., in the cowl, it can take some effort to flush it all completely out of the car.
Wiper pivots can leak water to the interior but not a LOT of water. For now I would assume the usual suspect, windshield gasket.