IMO BC raceway is a masterpiece, a classic among CE maps. I personally love it!
As for suggestions, the things that I can really think of are to make it where there are two or even three possible paths ,that are about the same length, that one could take to arrive at the next nav and also to make it where these paths intersect a path where the enemy could be going (if they're behind you or ahead or whatever).
You know, just a bit more contact, but make it a bit harder since there are a few paths. Like on Infinity at the oil refinery, you have three options, go down the middle, go through the right, or go through the far left.
And the second, just make one jump where you can get some major air (like the one on Death Island after the little jump/hill thing). I love catching mad air. = )
-nods- Other than that, keep up the good work! It's unfortunate that this will be your last map, but at the same time we always save the best for last!