Welcome chaz1138! I've got a '99 2.0 auto also. Just by slowing down to 65 or lower my avg mpg went over 30. I've been looking for the right rear wing, but I'm reluctant to drop $300+ on one.
Check out a really good New Beetle site with good technical info:
Homepage - NewBeetle.org - The Ultimate Resource for New Beetle Enthusiasts new