Source #1: Underside of rear carpet wet. Seal of vertical seam in back wall below corner of back window cracked open. Water from roof gutter drains into rear window gutter then flows right down this seam. Leak soaks carpet around lower rear seat belt anchor bolt, runs down under rear foot well carpet and drains into rear rocker panel gutter. Fixed by pushing silicone into hairline joint by rubbing sealant-loaded finger across the edge of the seam. Finish up detailing joint with small art trowel.
Source #2: Underside of front carpet wet. Positioning peg on back inboard seat anchoring bracket missing its thick soft rubber gasket. Undercarriage splash water gets in around the peg, seeps forward under seat into driver footwell, then outboard to front rocker panel gutter. Carpet backing has foam blocks that sit in the gutter marinating, never dries out. Fixed by installing 1/4" thick squishy rubber washer on peg, silicone around hole before dropping seat into position. An old neoprene mouse pad is good material for this gasket.
Source #2: Underside of front carpet wet. Positioning peg on back inboard seat anchoring bracket missing its thick soft rubber gasket. Undercarriage splash water gets in around the peg, seeps forward under seat into driver footwell, then outboard to front rocker panel gutter. Carpet backing has foam blocks that sit in the gutter marinating, never dries out. Fixed by installing 1/4" thick squishy rubber washer on peg, silicone around hole before dropping seat into position. An old neoprene mouse pad is good material for this gasket.