[sperry]

Good points, advancing the timing doesn't add o2 to the combustion, but on a N/A car, it's one of the primary ways to make additional power. On a turbo car, the primary way to make power is by increasing boost. Adding boost can result in detonation as described above because the additional o2 makes the fuel/air mix more volitile. As the Monkey stated, higher octane gas can help.

The Vishnu Stage 0 both advances the timing and adds boost. Timing is controlled by the ECU and the Unichip piggyback tricks the ECU into advancing the timing. The Manual Boost Controller sets a mechanical max for boost, and any attempts by the ECU to adjust the boost are lost because the actuator hose is plain old disconnected.

Stage Sub-Zero, tho it doesn't have a Unichip or MBC, does still trick the ECU into mild boost increases. But IIRC the biggest power gains are from the up-pipe and underdrive pulley.