High idle RPM

My 5.7 liter engine idles at 1400 RPM, driving the car down the road at 30mph! I have changed both gaskets on the intake manifold, swapped/changed idle air controller, throttle position indicator,mass air flow sensor, and checked for vacumn leaks with starter fluid- and,no, I did not catch it on fire even though it crossed my mind.Before I add an ignition source to the starter fluid, I would like to hear some thoughts on this problem. Thank You

I recommend having your codes read. Take the Caddy to your local auto parts store and they will do that for you. Check with your dealership also because there are “high idle” bulletins out there. The last one was issued on 19 Jan 2010.