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Do a search on here or on the web for "vented opti conversion" or something like that. Some of the hits will be about retrofitting the later distributor, but some are about adding vent lines to the early one, which is what the kit you link to is about.
If the picture at the above link shows all the parts provided then it isn't going to be a very good solution since you need two lines for proper venting.
The fact that it's listed for 92-93 is another warning sign that they may not know what they are talking about.
When I replaced the opti on my 92, I took the unit apart and applied blue RTV sealent all the way around where the two halves come together. Then I made the drain hole at the bottom of the unit slightly bigger. Seemed to take care of any moisture problems.