I'm not sure you've also caught this news as well:
Initial D Fourth Stage D Selection 2 will be released on September 28th, 2005
About the soundtrack giving indications, for 1st stage they did had 3 cds: 1 was til in the middle of r32 race cause 2nd disc has burnin up for you, 2nd goes til kenta's race, then 3rd stage was to the end of 1st stage. 2nd stage only had 1 for the 13 episodes. I also believe the nonstop mixes came out after the seasons were done and before the next one started. Maybe that info might help.