2006 Sonata 2.4l - low idle and code P2187
 

Hi everyone.
I have a 2006 Sonata 2.4l (70k miles) and I experience a low idle once the car heats up...I have the feeling the car would die any second but it doesn't.
I had a CEL that I checked yesterday and the code was P2187.
I replaced the air filter, spark plugs and cleaned the MAF sensor (they were on my list anyway), still the same thing.
I've read on the internet that it might be the intake manifold gasket...I sprayed MAF sensor cleaner around it, no change in RPM.
Now, 2 other possibilities I've read about were O2 sensor or Vapor Canister or Purge Valve (is it the same thing?). I just don't wanna spend money on parts that are not the issue.
Did anyone have this issue before? Is going to the dealer and have it scanned my last option?

Thanks a lot.