w124-benz

Hi Guys. I just bought a 1999 E55 a few days ago and am truly loving the drive. However, upon detailing the interior the other day, I decided to pull up the backseat and I found a bit of water under the seat on the drivers side (left). It wasn't a lot, but the insulation material was fairly saturated in that area. I have since dried it out and completely removed the rear seat, including the seatback and insulation pad.
The water seems to be running down from behind the drivers side C-pillar and down under the rear seat.
I have since cleared out the front sunroof drains with compressed air but was unable to see if there are any rear drains for the sunroof. Any ideas on where the best access point is for the rear drains for clearing them?
Any other ideas on where water could be getting in from? Thanks a bunch!