If you haven't swapped out the PCV valve in the last 3 years, you might try it and see if it helps -- even a little. My new-to-me 1994 Celica had low idle problems to the point it flat out died at a stop sign idle on time.
The PCV valve and its gasket were pretty obviously damaged (rocked all over the place indicating no real good seal). I replaced it with new parts for less than $10, and the fix was quick and easy. Just install the PCV valve into the gasket before installing both into the valve cover.
I also cleaned out the MAS sensor and air
Intake using MAS sensor cleaner for both.
It idles much better now. It has about 335,000 miles on it, and wasn't exactly maintained very well as indicated by the clogged PCV sensor and oil caked all over the underside of the vehicle, but she still runs pretty good and might have a few years left in her if given some TLC.
It would be nice to get it to at least 400,000 miles.
