w0w you read it in japanese?
I also read this manga a lot of times..IMO it's one of the best Adachi's work..The ending is great..I think Adachi's decision to make it left-off is wise..because it's somewhat cliche to let Yamato win the competition and to let his rival win would make the readers dissapointed, moreover it doesn't really matter whether Yamato or his rival who wins. What's important is Ami's decision, which is presented by Adachi in quite a way..