Whats the size of the BungHole in question...I have heard that with a larger bunghole you don't need the bunghole lube, but if you have a tighter bunghole it is an absolute must... The last thing you want to do is tear a new one into the downtube if it is a tight fit.
Since bunghole size is unique to each situation, and how each bunghole has been used/abused, any new insertions into any bunghole should have some form of lube. Mark
*Update* This whole bunghole thing was making me a little nervous, so I called Naterbob again (yep, charged me 20 bucks), and he's sending me a gerbil at cost (60 bucks, better be one nice looking gerbil), and he gave me a 100% guarantee the gerbil properly inserted into the bunghole will fix the problem, unless it doesn't. I'm not sure how sticking live rodents into my car's magical bung is going to help, but at this point I'm willing to give it a shot...
Make sure they send you the Richard Gere instructions...apparently they are easier to follow as it goes through an informative "HOW TO" step by step process with pictures