Gas throttle is sticking rpm is high

I will try to explain new electronic injection. There is an adjustment but you have another problem if the idle speed is too high.

When the RPM goes higher, it means you have an air leak, intake runner problem or higher fuel pressure than the stock setting. Or ISC (idle speed control solenoid) Think of it like opening the throttle slightly and letting more air into the motor or gas into the engine.

You can use a pump spray bottle of water with the engine running and mist the seams and vacuum lines and switches. A change in RPM indicates a leak.

Intake runner. These are like shutters inside the intake manifold. Modern intakes can have 2 levels of airflow separated by the intake runners. Sticking runners can let more air into the engine at the wrong time and affect idle.

ISC solenoid Is a valve that regulates airflow for the idle. Soot can cause it to stick in the wrong position. Removing and cleaning the port with WD40 can help.

High fuel pressure. If the fuel regulator sends more gas to the engine, the RPM will increase.

There is a set screw at the base of the airhorn to stop the throttle cable. It is called a throttle stop. There is a hex hole for an allen wrench and it has been coated with threadlock in some instances. Really it is not meant to be turned once the factory sets it. But you can do it. If anything fixes the defects I mentioned, the idle may be too low. I do not have the Specs or know if you have any optional engine. Generally the engines idle between 525-and 600 rpm.

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check to make sure the throttle valve Is not sticking open and not fully closing as this can cause a higher than normal idle. check to see if its dirty and clean it with throttle cleaner and a tooth brush this will allow the valve to close and not be gumed up. another thing to check is for a vacume leak like maybe a bad pcv valve. just some places to check out.

You don't say if the engine is carb or fuel injected.
If it has a carb, it could be sticking linkage for the fast idle to the choke.
If it is fuel injected it could be a faulty idle air control valve.
Or it could be something holding the throttle open like a binding cable.

The spring that returns the throttle is getting weak. Best thing to do is clean the throttle inside and out. Clean the throttle plate front and back and as for as you reach inside, use an old tooth brush and brake clean. Once clean lube the spring area. This should help. But if it still sticks , I would be looking at the throttle cable.

Assuming you don't have any stray vacuum lines, I'd look into the TPS (throttle position sensor) Most idling problems can be traced back to the TPS.

you didnt say if it was happening only during the initial warm up of the vehicle or all the time. if it is just during warm up this is not too unusual as long as the engine isnt racing. if it is just a "high idle", say arround 2,000 rpm's its normal. the idle would usually go down as the vehicle reaches operating temperature. when you put the vehicle in gear, you are actually loading the engine slightly, thats why the idle comes down then. when in park the engine has no load on it so it is free to rev a little higher at these times. if it a at a high idle constantly, then i would start looking for sticking throttle cable, binding throttle plates, ect and remedy the problem. this should not have anything to do with the dual exhaust.

you need to replace the throttle position sensor on the intake.

None of those possible problems have anything to do with idle speed. The first thing might be a very weak throttle return spring. The next would be a sticky throttle cable or foot feed pedal that isn't moving freely. Another possibility is a vacuum leak somewhere. Did changing the spark plug in #1 cylinder help the misfire? If not, you may have a partially plugged injector. Fixing the misfire will only increase idle speed some more. Look for an idle speed motor near the throttle body that is supposed to raise idle speed when the engine is cold and lower it back when the engine warms up. Check to see if it is holding the speed too high. If the throttle position sensor tells the computer where the idle speed motor is set, then it could have an effect on idle speed if the sensor is bad. The position sensor is just a fancy potentiometer. Hope some of this helps.

Check your vacuum lines, make sure there is no leaks, and go from there, then all you electrical connection in the engine compartment.
I have a 1996 Jetta Trek Edition, the hoses, and wire harness, are so brittle, any movement can cause hoses and wire insulation to crack.

Check your throttle position sensor