Rough Idle: 500-800 rpms

I bought a 2000 Celica GTS with 155,000 miles on it (a lot I know) and so far I absolutely love it! I've had it for about a month now and fixed most of the minor issues. The issue I face now is that my idle is really low. I seafomed my Oil (yes, I changed my oil), Gas, and Intake; which helped a little bit I guess. I haven't noticed any vacuum line leaks, though I'm not always sure which are vacuum lines and which are coolant lines. I also replaced my spark plugs and Air Filter. I reset my ECU and it hasn't seemed to help other than it doesn't try to jump up again by kicking on the radiator fans, which is what I noticed it does when it tries to save itself from dying. One last thing, when I got it the MAF threw a CEL which I fixed by cleaning the MAF.

So my questions would be: What's your average warm engine idle? Have you experienced this issue? I've read someone suggested to clean my throttle body, does that sound right? Lastly, any suggestions?

Thank you for reading! I love my Celica!