None of you guys have figured that one out. This one drove me nuts. I bought a 94 GSR and the first big rain the trunk and the interior filled up with like a inch of water. The guy totally screwed me. It turns out it's the sunroof. Apparently all sunroofs leak so they install a gutter around the seal and then run hoses to the front and the back. The problem in the hose design on the Integra has a the stupidest lip and as you drive around and get leaves stuck in the gutter of the sunroof which later decompose the sunroof hose clogs. Well once it's glogged the rain seems to like to go the trunk. Consider yourself lucky that it hasn't go to the interior yet. I went out in the rain and watched the water dripping from my drivers side visor. Now a Helm's manual is going to be the biggest help here, but you can do it without one. Open up the trunk. Remove the plastic covers for that give you access to the lights. Then remove the whole large plastic part that runs along the back of the car (the plastic pins are like 50cents each at Acura when you put it back). Now there are two large plastic parts on each side of the car that run all the way into the back seats. There might be some screws here, but what you need to do is pull them out partially. It's a real pain to take them out all the way, but that would be best. That would involve taking out a few bolts, and the entire back seat. That's what I did. Once you get these things pulled away you're going to notice that there's hosing behind the panelling on each side of the car. The one on the drivers side connects into a T and gets water from the power antenna motor too. Pull the hose out and there's a black part that actually connects into into the body of the car to drain. Cut the tip of this so that it wont glog up with anything more. Make sure to clean out the hoses too. Then put it all back and you shouldn't leak anymore. I'll try to get some pictures up. I took a few of how I cut the stuff etc etc. I really should make a how-to on this. It happens to a lot of people with Integras.