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Hello, I'm sorry you haven't received a reply sooner I hope the following is of assistance.
This engine is a little prone to air leaks into the intake system, this leads to an increase in idle speed, the idle speed can also become erratic as the engine management tries to compensate for the excess of air. The most common cause of an air leak is a split in the crankcase breather hose that is connected to the inlet manifold at the bottom, you can try to pinch the hose with long nosed pliers, if the idle speed acts as it should then this would confirm a split hose, you can access the hose between the inlet tracts on the manifold between cylinders 3 and 4 but if the hose needs replacing it's easier to remove the inlet manifold to replace it.
There can be other causes of an increased idle for example a throttle position sensor fault but to diagnose any sensor/actuator concern requires a diagnostic scan tool that ideally can read live data as well.
Start with checking the inlet system, let me know if I can assist further or if you have more questions regarding this and I'll reply as soon as I'm able to.