CB7 should be more or less the same as CD5.

I'd be looking at the aperture where the top of the coilover penetrates the top of the tower. Perhaps water spray is leaking in at this point, and then trickling down the 'outside' of the tower? (the 'outside' of the tower being on the inside of the cabin).

There is (or should be) a rubbery ring at the top of the coilover between the coilover and the top of the aperture. This ring seals the aperture to dust and water. Perhaps this has perished?