Here's a great way to get a low lap time on TIME TRIAL mode. Start the trial, and save your turbo boost for the whole lap. Right before you cross the finish line, use the turbo boost. This way, you're going really fast when you start the next lap. Plus you get a new boost!
To get the Pirhana 2 racing team, get any award on all six time trial challenges. This team is maxed out in every category.
To get the Cyclone option (makes each weapon twice as powerful), complete all six weapon challenges and recieve ANY award on them. Go to the Options on the main menu screen. Then go to the game configuration to turn Cyclone ON/OFF.
Finish Wipeout 64's "Race" competition by getting at least "bronze", and you will be able to race on the hidden track, Velocitar.