About 40,000 miles ago my 2005 accent started running really rough and sometimes would not accelerate. I pulled the code P0121 which calls for a bad TPS. I checked the sensor and the resistance was in range. It still didn't work so I replaced it. The symptoms didn't get better. At the same time my aftermarket head unit started to fail. After getting fed up with it I reinstalling the factory headunit and the car went back to running like new. I cleared the code and it didn't come back.

Fast forward to today and now all the symptoms are back. The sensor still reads in the correct resistance range and the car runs bad. My fears are that I have electrical issues that will result in big repair bills. Is there anything obvious I am missing before I take the car into a repair shop?

I have changed the oil every 3K, air filter every 20K, tranny fluid every 25K, spark plugs every 25k. I replaced the in tank fuel filter 23K ago.