Supercharged Vx idling too high

[M6ltr]

Apologies if this has been asked before(new to this site) but what could possibly make a supercharged vx commodore idle too high?
Short story is..The car was dropped at a mechanics for a blue slip.Was stored there for a few weeks with the owners permission due to moving and having no secure storage. When it was picked up,the engine sounded very different almost like it was going to blow up and was idling too high.The car did not sound like this when dropped off for the blue slip.My first thought was someone has took the car out and gave it a good thrashing.That’s what the sound reminded me off.
I have since found out that,it possibly could of been taken out and thrashed around and has had a oil change and new oil filter while at this workshop as it has nice clean oil in it where as before it was old dirty oil.They were not asked to do anything apart from a blue slip.
My question is..if it was taken out and had the crap flogged out of it,could that have done some kind of damage to make it idle so high?

 

[Brysha89]

no it wont make it idle higher if they took it out and thrashed it they could have done something internal which you would hear ticks and knocks the idle would probably be ether a loose or broken air hose around the back of the charger forgot the names of them there small and go from the valley to the heads behind the engine, Also the mechanic would of seen the oil and done it free if its not on your receipt as black oil is bad, recently on a side note i put my wm statesman in for a rwc in vic and they picked on bad brake fluid so maby bad oil is apart of the blue slip now days

 

[Brysha89]

also you said it was left at the mechs for a few weeks while you moved house the hoses could have gotten brittle and when you started the engine could of cracked them your self as the engine dose shake side to side slightly as it kicks over

 

[gossie]

Have you discussed this with the people you left it with?
OH PLEASE.

 

[z900collector]

Vacuum leak??? - check ALL the hoses and check the IAC solenoid/stepper... might be dirty?