i have a 99 miata that leaks on passenger floor. i think it might be three issues but am not sure. first noticed after rain but then noticed while driving in summer rain water pouring in under passenger side dash when you went around a corner. also leaked when a/c was on. Dried it out. Parked on side of garage for a month and came home to find right side passenger floor flooded with no movement or a/c. Drain from cowl basin down fender side is clear. so this leak might me a/c or body leak. Secondly, low performance cat converter, should i replace cat only or invest in performance exhaust. any guidance and support is appreciated.

 

There is a drain pipe on the firewall that gets clogged and the water ends up on the passenger floorboard. If you blow compressed air or otherwise unplug it that will likely solve the problem.