Water sound coming from behind dash

After a bad rain storm, I heard water that appeared to come from behind my dashboard. Been going on for about four weeks. Sound of water is most prevalent at a cold start, when I accelerate/reverse and less as you started to drive and the car got warm. We took off the grill and cleared the cowl's. Only the driver side had the rubber plug/drain, the opposite did not have a rubber plug/drain. Both sides were really clogged and there was some standing water. After vacuuming up the leaves and unclogging the plugs, the water rushed through and fell to the ground. We thought we solved the problem. Put everything back together and got in my car the following morning and when I start my car I still hear water behind my dash board. Not as much as before, but it is still there. When I accelerate, I also hear water sloshing about. It is not dripping inside my car nor do I see it on the ground? I do find that the car does drive a bit more sluggish since, so I am confused on what to do/look at/unplug at this time?