I just bought a TPS of someone and put it on my car, I have heard there is a way to set it somehow so that the idle is right but you have to use a voltmeter or something like that. Does anyone know if thats true and if so or not can someone let me know how to set it correctly?

 

Here is how I calibrate my TP sensors with it out of the car. You can calibrate it in the car but you'll need T-pins to backprobe, then you have to tighten the two screws and theres barely room to tighten the screws. I have done it out of the car numerous times and it has been perfect. First familiar yourself with the attachment. You'll need a DMM (Digital Multi-Meter), a spare plug for the sensor or a couple of jumper wires with alligator clips.
1. Bolt sensor onto the throttle body and tighten it to where you can still adjust it.
2. Set your DMM to measure ohm resistance from 1K (1000 ohms) to 5K (5000 ohms). I had mine set at the 20k setting.
3. It doesn't matter which lead goes where but positive lead of DMM to the pin colored in yellow and black lead to pin colored in red.
4. I have measured many TPS resistance this way and I have found that at idle I get a ohm reading of 1.01K and at WOT the reading is 5.36K. Adjust the TPS until you get ~1.01K ohms and tighten the screws. Once tightened go WOT and the reading should be ~5.36K ohms.

In less than 5 minutes you're done and ready to bolt it on the car.