take a look in the write-ups forum, I posted a full description of what it took me to win that race.
It is a tough race, and yes, you do need to fully outfit the vitz to stay competitive. Preserverance is key to winning.
As for racing diryt: take it easy on the bumping and pushing, as the AI rarely lose their line. However, if you opt to race dirty, take full advantage of blocking them from passing, and indeed forcing them into a barrier.
AO