OK, thank you all...
Stevo, I had already checked for some airleak.
The car drives perfect on all other ocasions: idle at cold is just over the lower dot, and just below the upper dot when warm. When I hit 3500 RPM, it looks like some jumbo jet just hit my rear bumper!
I have a free day tomorrow, so I'll have time to check the TPS problem. What value should we read on the computer?
Other question: is an RS500 TPS the same as my RWD Sapphire's?
Thanks again!
Yes, they're the same - they are marked PF01.
Output voltage from the TPS should start at 5 volts with zero throttle, then step to 4.5 volts before falling down linearly to 0.5 volts at wide open throttle. The diagnostic function of the ECU will only log a fault if the sensor's disconnected, or shorted, so you do need some kind of constant monitor so you can spot the fault when it happens. A passenger with an analog volt meter would be better than a digital meter for this purpose, and a proper engine monitor would be infinitely better than that.
Ideally you need to constantly monitor the output of the sensor while you're driving it - it will be difficult to reliably test it while the car's stationary as chances are there'll be no fault unless the vehicle's actually moving.