the latest cap version is .04 but generally speaking, the .01 thur .04 designs are very similar. The .00 design was vastly different and very weak (had a rounded inner flange).
If you've already checked under the carpet and barring any other signs of a leak, and if the cap is on tight (the p/n should be a the 6 o'clock position when standing at rear of car) you're in all likely-hood good to go. For the sake of argument though, remove the coolant cap, oil filler cap, and black cover plate below them (it'll pry right up) . Check the coolant tank bleeder valve (a black cap w/ what looks like 1/2 of a binder clip on top) and make sure it's in the down/locked (parallel to the road) position and there isn't any (more than a possible trace) white residue around it. If in doubt, you can have (almost any shop) run a quick pressure test on the cooling system (about 20min).
FWIW, I used to get similar condensation occasionally, depending on climate conditions, w/ my '99 Boxster but never had any issues.
