not a hard job to see where its leaking in just remove the front seat and the rear bench, undo the plastic sill runner and then lift out the carpet and under floor sound deadening, start your car and let it get upto temp and see where the water is coning from, if your heater are mint warm and no water coming down from heater matrix my guess is that 1 of the bulk head bungs has come out and it leaking water in from around where the pedal box is quite a common problem when previous owners have fitted cabling or boost pipes and not fitted them through the rubber bung. you get a 2" hole right below the front strut top that water runs down and right in to the foot well