Yes, the TPS can be calibrated using a volt/ohm meter. The TPS is simply a variable resistor, and depending on the angle of rotation, the resistance changes. Such sensor are very sensitive to poor soldering and connection problems, because such things will increase the resistance "seen" by the ECU, and will give a false reading.
This is basically what that bogus 20 HP RESISTOR MOD!!! you see on ebay does, only with the IAT sensor.
Anyway, I´ve got a 91GT, and you can adjust this very eaisly. The throttle pulley hits a little rubber pad which is damped by a small unit that looks a little like a hat. The throttle pulley hits this rubber thing with a little screw that you can adjust, just make sure you loctite the screw so your setting sticks.
If you want to kill the throttle more when you dead pedal it, you should turn this screw CW (in) so it will hit the rubber pad when the throttle has rotated MORE, and the butterfly valve is more closed. This will drop your rpm to idle speed faster.
The reason why mazda did this was to keep the momentum of the engine up during shifting... it´s a thing called a dashpot, which is a fancy name for a buffer.
Be careful when adjusting though, because if you make it so you dead throttle it too much, you will kill not only the momentum of the engine and the intake air, but you will also likely reverse the power transfer back to the wheels, which could potentially send you into a skid if you´re really pushing the car to the limit of the tires.
Also, you may want to check the ignition module. Mine is going bad and it´s very likely that yours is too. It is common to have an rpm drop, plateau for about 3 seconds, then drop more and fluctuate for another 5-10 seconds before settling out at idle speed.