Emulator: VBA-RR v23.6 svn480
I don't actually know if these two laps with the Fire Ball in Bianca City - Stretch Circuit (28"18 and 23"67 in the first Pawn track) is any good for TAS. I haven't found any ridiculous speed tricks, though.
I did mess with the in-game controls (to type 6) so that up triggers the boost instead of L+R. L and R buttons do a pretty good job at making you go a bit faster, especially if you're holding one opposite of where you're turning. Freezing this helpful boost for a few frames waiting for the boost to trigger is one way to slow you down, so I shift controls to the less-used up.