I have t-tops on my 86 iroc but they are not leaking. The water drips right above the rearview mirror. Very noticable during a hard rain. Does anybody know what is above the headliner right there that can leak.

I posted a picture of my headliner a while ago in a thread called water in car under interiers.

 

there are holes underneath the t-top bar in the roof that serve absolutely no purpose to my knowledge, but when that bar is to be installed it's waterproofed around the edges, i'm guessing that the waterproofing stuff is shot, you can either half a$$ is and try and get sum windshield sealant in a tube and pour it down the cracks where rain would end up, and let it fall in there and harden, do a couple coats, or you can go through the pain staking trouble of removing the t-top weatherstripping which you chance ripping or tearing if it's old, then removing the t-top bar, make sure there is no rust underneath the bar or on the roof, get new sealant around the edges, re-install the bar, and then re-install the weatherstripping. Personally i would suggest the windshield sealant, i had a windshield on my '91 cutlass that was BAD at the top, did 3-4 coats all the way across the top to the point it was smooth, molding to roof with the stuff, it doesn' even think about leaking now, it's perfect. And that saved me a very expensive windshield sealing job, all for around $3-4 dollars. Your choice really.