Intake manifold gasket

[Gun40t]

Hey guys so for ages I have been tryna find what is wrong with my car I have scanned it no codes, but I've lost power down low abit it idles like sh*t to the point it nearly stalls, I have looked for leaks and cant find anything I probably need to go get a smoke test, the idle gets worse when air con is turned on, I can hear hissing in the engine bay, under the impression it's the aircon lines, I'm ready just to go and buy a gasket tomorow and fit it up I have also been told my a mechanic that there was oil coming out of the intake manifold which I found odd. But I had a faulty pcv at one stage which I replaced, could be crank case pressure not sure, if anyone has any ideas.

 

If not and you think the same issue please give me some info on changing it. I have more tools then a snap on truck so I will be able to do the job thanks guys.

 

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