Sprinkle baby power around back there. Dripping water leaves tracks in the powder so you can see where it comes from. I assume that air-outlet vent is still a strong suspect...

 

Get in the trunk with a good flashlight. Close the trunk.

Have an assistant apply water with a garden hose first at the trunk drain channels while you search for leaks.

Then apply water higher up at the sunroof area.

Look carefully at the taillight wiring/socket area.

 

Sorry about being so late for responding. I really appriciate all the help, guys. I pulled the carpet and "sides" out of the trunk, and found that it was leaking from the passenger side rear tail light. It's collected, and gotten some mildew under the ABS computer- what a shock that it doesn't work. The water ran down the side of the trunk, into where the spare tire was. The spare tire kept the water from sitting in the very bottom, but I wiped it all out.
Now I just need to pull the tail light off and put a new seal in! I'm going to check my sunroof tubes anyways- I didn't pull the driver's side stuff off, since the computer (and presumed leak) was on the right.
Thanks again for the help!

 

So I ordered new outer seals from Honda, pulled the tail lights out, and replaced them. However the trunk is now leaking from a black plug located on the back of the trunk. I had someone spray the seam between the bumper and trunk and water leaks from the plug. Pictures are attached showing the plug and where I spray water. Do any of you know why the holes are there? If I order a new plug, do you think that will fix it? Additionally, water has been collecting in the trunk latch plastic. What else could leak and cause that problem?
Thanks again for your help!

 

Not sure why the hole is there, but a couple possibilities...

For trailer-light wiring, you replace that with a grommet for the wires?
For alignment fixtures when they're assembling the body?

You ought to be able to seal around that plug with some caulking.

 

Dude! Just fixed this problem with lacer thinner to clean and silicone all the way around the perimeter of that box and over the white clips around it. I let that sit for a day then had my son hit the trunk with the hose from all angles and found it to be as dry as a popcorn fart.. That is my 92, but my 91 has a leak around the taillights. new gasket is on my list.

 

I replaced these 2 plugs and they don't leak anymore.