[mn box s]

I'm not 100% positive on boxsters because I havent had mine too long. I'm going to asume it is like most all cars. Pull the battery and then the tray that the battery sits on. Or look in the corners of the battery compartment theres got to be a hole 1/8-1/4" hole which would have a plastic hose which you probably won't see but would carry any water out near the A-pillar somewhere. Jim, correct me if I'm wrong thanks.

You don't think this was from the battery before you washed it do you? Battery could be bad causing your electrical to go funny at start up, then works fine once you are using your alternator?