I warm the car up and adjust the TPS (I use the twin test light method); ground the test connector and adjust the idle. So far so good. But then I drive the car around the block and retest the TPS adjustment and two lights are lit. This happens over and over again. I can't ever get it to stay put! I've ruled out vacuum problems because it maintains a steady 17". Rev the engine and it comes right back to 17". What am I doing wrong here? What do I need to check or adjust to fix my problem?

 

Try using the resistance/voltages tests. If those still suck, I guess you need a new TPS.

 

Check with a multimeter (resistance) to ensure travel is smooth and no spikes or drops. After you verify quality of TPS, set at 1k ohm, then do final adjustment via light method.

 

Just because you're reading 17" does not mean you don't have a vac leak. She's going to suck around 17" of vac, no matter WHERE the air is coming from

Check the TPS at the ECU input pin, it's the ONLY way to verify that the entire system is working and the ECU is seeing what you want it to see.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/troubleshooting-your-car-ecu-340578/