66 slant dart, running the supersix setup. Been running real good. Got my idle dialed in. Now recently, outta the blue, I start the car and the idle is way high, 1200rpm. And no matter what I do, tap the pedal etc... it wont drop down, and in fact is very slow to reduce RPM to 1200 even. I open hood, and mess with things, nothing helps. I mess with throttle plates, close them and engine dies. Then restart and it is fine , meaning cold idle is at 850 at park. This has now happened twice. Any idea what is going on? something inside the Carter BBD?