I had water in my trunk also. What i did was take the lights off sprayed some spray adhesive on the back of them and silicone the top where the rubber stops are for the trunk. Around the black thing. Kinda hard to explain.
98 CSVT Black
Alpine CDA 7995
Memphis 1000D & Alpine MRV T302
2 Orion 12's
HPP Rear Strut Bar