I've been hunting (or is that haunting?) for Halloween chips extensively. As far as I know there was no 4Q chip issued for Halloween in 2001, with or without Elvira.

I think Mark answered the question in this post:
http://www.thechipboard.com/cgi-bin/tcbarc10/tcbarc10.pl?read=294956

"that would would make for a fourth variety"
I'm interpreting that as referring to 2004.