Since I no longer have my FCV (thanks to weeks101) I have wanted to find a plug for the connector that is left open. I found one here: http://www.automotive-connectors.com/5w9t-14a594-aa-4-way-sealed-male-cover-1-5-mm-1-row-coding-i-neutral.html (They are based out of Germany)
This will keep dust/dirt, oil, corrosion of terminals out of the connector. I received mine today and installed it.

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Phil
2005 131k 3.7 Gasser (Lifted-CRD Springs, 4.10 Gears, F+R DTT, Teraflex 2wd Low, Skidrow/Mopar Skids, Rock Lizard Super Skinks, Goodyear Wrangler Authority 31x10.5-15)
2012 Triumph Tiger (TKC 80 Front Tire Heidnau K60 Rear, Crash Bars, Skid Plate, Bark Busters, Pelican Case Top Box)