Rain water leaks !!

Sixthfinger57

When it rains, my 1996 Grand Marquis front drivers/passenger floors gets wet, occasionally rear floors. AC drain is not clogged, water drains in cowling all clear. Windshield is secure. Rubber door gaskets are good. It seems that the water is coming in somewhere on firewall. Took plastic cowling completely off, don't see where it could be leaking. After I take the cowling off, should I also take the windshield wiper motor assembly off to completely get to as much of firewall as possible? I am at my wits end ! Where is the water getting in???