RPM going stir crazy

175K miles on it, It struggles when trying to turn it on. After turning the ignition, starts off with rpm dial going up, and down several times, then chokes. Once it warms up, it idles after about 2 mins of warm up. When driving, it is smooth, until you release the accelerator. Then the RPM dial goes nuts and fluctuates, from 0 up to where it should between 2-3 k RPMs. I have taken this to the dealer and other mechanics. Each one is telling us different. Is it the exhaust manifold, throttle body control, catalytic convertor!

If you want some useful answers you’ve got to tell us much more specific info. Basics like year of the car, size of the motor, recent maintenance, last time spark plugs were changed, how long the problem has been going on, is the check engine light on? Stuff like that.

Is it just the dial jumping around or does the engine speed actually jump around?

If both it’s probably the coil or igniter.
If it’s just the dial then it’s the gauge or the wiring/connectors to it.