i had the same thing in my M Tech II
under the fusebox by the firewall is were my car was rusting, pull the carpet back from the pedal area untill the shell is exposed, have the hood open and look up, and you will more than likely see sunlight, i had about a 2 inch hole that had rusted through. not fun.
its kinda hard to see it from inside unless you have moved the fusebox and carpet out of the way. check it, from what i understand, its somewhat of a common area, thin wall and will cause the same issues as you described.
good luck and I hope that yours isnt as bad as mine was. or heck i hope thats not the case at all and it just a seal that can be replaced or something.
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