First off, I'd pull down that CEL check plug on the passenger side sitting above the ecu. Jump it with a paper clip, turn your ignition to the run position, and watch the CEL flash your codes. Long blinks are 10s and short ones are 1s.
Eg: Long, Long, short, short, short = code 23
I would guess you're throwing an Iacv code or map sensor, or heated 02. If you aren't throwing any codes, check your coolant level. If your idle is hopping up and down, you may have air in the system. One really easy way to check for intake leaks is to get a can of ether (aka quick start) and sparingly spray around your vacuum lines individually. If you have a leak, chances are your rpm will increase on its own. You don't have to rep me lol! Best of luck, pm me if you like with any more questions.