Hello, please take a look at attached pics of the windshield cowell and let me know if this could be the cause of a substantial leak coming in at the passenger firewall area

 

The electrical tape and what appears to be a gap at the base of the windshield could be a issue...

 

Doubt it's directly causing your leak as cowl doesn't really provide a good seal. There may be an accumulation of misc. crap beneath the cowling that's preventing proper drainage or directing water into cabin air intake. AB has a good video on removal if you decide to take a look under. My cowl has a couple of similar issues, not causing any leaks and when leaves are falling keep it cleared out.


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That cowl crack... Does it extend to the air conditioning intake that runs the entire width of the hood? If so and if your drains are clogged, you would have substantial water leak in the passenger footwell area. Same as if you had clogged drains and were using your air conditioner.

You should try poking the drain nipples under the truck. If they release alot of water then you'll know the drains are backing up and you can figure out why.