Jason> I have the exact same car that you do, same year too. I also have 15 years experience as an auto glass worker, which included finding leaks in cars of all kinds. Granted, this was years ago, but I have some thoughts for you regarding finding trunk leaks you might benefit from, so here goes. WARNING: This is going to sound ridiculous, but it is really the only way to find them.
Rule No. 1: Water usually runs downhill, rarely uphill....so if there is a hole somewhere in the lower portion of your car, it rarely splashes up INTO the car. Yes, it can happen, but it's rare. Consider this only after everything else has been tried. The only real way you can pinpoint a trunk leak is to get in the trunk. That's right. Get in the trunk and close it. Obviously, you will need a few things.
One, a flashlight since it will be pitch black. Then, a good friend who is willing to help. And, finally, a garden hose with NO NOZZLE on the end of it. You're not going to water the lawn here, you're finding a leak, and you don't want to "spray" anything. Take everything you can out of the trunk incl. the spare tire and any mats or covers, etc. Make sure it is bone dry by wiping it with dry towels. Have your helper turn on a garden hose on gentle stream, NOT spray. Get in the trunk and have him/her close it. Now, this is the most important part. With you in the trunk, and the flashlight on, knock on the trunk lid so the person outside can hear you and that will signal them to start running the hose over THE LOWEST POINT OF THE TRUNK LID. Have them start at the bottom of the taillights and work their way across the bottom of the trunk lid, checking the gasket, etc. Then have them work their way UP slowly. VERY slowly. If there is a leak, you will see it running in. If it runs in, knock on the trunk lid and have the person open it up.
If it's not leaking down below, have them move the hose up to the top of the trunk lid on each side, allowing the water to just cascade over small portions of the trunk. Nothing yet? Then move up higher to the backglass. As you can see, the whole idea here is to work UP slowly, othewise if you wet the top of the car, you will never know where it's coming in. Windshield leaks are found the same way, by the way. If you're a big guy, have a smaller person in the trunk. Go slowly and you will find it. If this fails, then start looking for any way the water can be splashing up from the road and getting in the trunk. Hope this helps.