Need help! Idle problems.

[Bow_02Si]

I have a stock k20a3 with bolt ons, recently my RPM has been fluctuating between 800 then revving back up to 1200/1500rpm then repeating over and over. It usually occurs after driving on the highway, but now its getting worse and happening almost everywhere. Was told there might be air in my coolant so I flushed it and problem is still occuring. So I tried cleaning out injectors and fuel system and problem is still occurring. Do I need to replace the IACV? If so is there a DIY or a guide anywhere. I'm in experienced with these problems so any suggestions will be helpful.

Thank you.

[zdiddy22]

It could be a number of things. The iacv, gasket, or vacuum leak. Make sure nothing broke when you put the intake on. Then check iacv.