Thanks to my roommate forwarding me a link to a picture of another series done by Shigeno, I did a little random poking around. The title of the manga is Sky Blue Coming Out Of The Tunnel, and is a one-shot story (i.e., there is only one volume, not a continuing series.) It revolves around our hero, Ishizaka Nobuhiko (I think I'm reading that name right...). He works at a resort hotel at the beach during the summer, and drives a panda Trueno (AE 86). Chiharu, a classmate of his, confessed that she is interested in him. But he only has eyes for Maari, a girl from Tokyo, who is working at the hotel next to his.
There is a car race, the 86 vs. a Z32, downhill. But there is only the one race. All of the reviews I read commented that the races were not as well done as those in Initial D. It was published in 1992, which puts it in the span of time between Baribari Densetsu and Initial D. It looks to be the work that he did just before Do-p-kan.
The people who read the manga who were commenting on it said that it was primarily a romance. Several people commented that at first they assumed that it was a forerunner to Initial D, since the hero drives a Hachiroku. But reading it, they thought it was more a forerunner to Do-p-kan, since it is primarily a romance series. Several people also commented that it seemed like the regrets of the main character were more a self-insert on the part of the author. Gee, we've never seen Shigeno do a self-insert before, now have we? ^_^
The most useful link from my research is here. Though I suppose it's not too useful if one's browser doesn't display Japanese.
Just because it's sticking in my mind at the moment, Bariden ran for 38 volumes, and Do-p-kan ran for 10.