Glad you asked this, and glad to hear Ray's response. I was at the Ground Kontrol classic arcade in Portland today (awesome arcade btw), and played a pac man cocktail that was fast. When I got home, I went into the dip switch settings in mame to see if there was such a setting (and no, there isn't), so I was wondering what was up with that.
I'm interested to see (maybe someone knows off hand) if there are clones of pac man (or galaga) that have these hacks.