Is your carpet getting wet in the front on the passenger side?
 

mine was, someone ruined the grommet for the harness that passes through the firewall. luckily the parts guy at gm took the time to find the engineering number for it by calling gm and was able to order one! it was a pain in the ass to install due to the fact the hole the wires go through is the size of a pencil so the two connectors need to be de-pinned. i put the wires through one by one, when it was time to slide the grommet up the harness i sprayed the harness with silicone spray, made life alot better!

anyway i wanted to post this for anyone else that has the same issue. this grommet seals the firewall under the pcm, right where water runs down the strut tower/firewall. without it it runs right into the car.

the part number for the grommet is 22709699

last pic

I literally covered mine in silicon after I ran the wires for my gauges. no leak. Nice job that takes some patience