I had that problem on my 89 V6. There is an o-ring that sits between the distributor cap and the distributor body. There were only fragments of the original when I purchased the truck. The o-ring part number is MD611460. I opened up all the electrical connections and sprayed some contact cleaner/lubricant on the contacts. Once both of these were done, the hard starting in damp weather went away.

Mitsu # 6 - 98 6G72 Montero Sport, Locking Rear Diff, Aisin Manual Hubs, 31x10.5

Mitsu # 7 - 02 6G74 Montero Limited