Located at top left of the picture in line with the butterfly spindle engine side (black three pin connector).
The TPS is a variable resistor, with a wiper which moves with accelerator pedal position. +5 and 0Volts is supplied by the ECU, the wiper output therefore varies inside these two limits.
The ECU uses the TPS for information on the position ie. idle,wide open throttle or high rates of change of the accelerator pedal. Additional fueling will occur under heavy acceleration, on overrun however the fueling will be cut off above 2000RPM. This is gives greater fuel economy but is extremely boring as this restricts the amount of pops and bangs emitting from the exhaust (R300/400/500 don't seem to have this problem!)