Although the fast idle screw location is almost out of the picture - it is missing. You can see a threaded hole in the bottom right hand corner of the image on the underside of the throttle linkage. Yeah this carb has fallen foul of the dreaded 'Mikuni fiddler'. All the brass screws in the center of the image don't need to be touched as they are metering screws. You are correct with the air bleed jet and the air/fuel mixture but the one labelled 'choke' is the throttle stop adjust screw. The 'secondary' screw is another stop adjust screw that should be sealed with paint from factory. The only time when someone starts messing with all the settings is when the carb is either due for an overhaul, it got a gutfull of debris and the jets became clogged, or the secondary vacuum unit or auto choke unit has failed and they didn't diagnose the failure. These are not a nice carb for a novice to work on. It would be at this point I would suggest finding another carb that hasn't been tampered with, buying a kit and go through the rebuild process by the book. Keep in mind you have a 4G52 so you're going to need another carb from a 2.0 liter engine. If this is on the verge of impossible you might be able to use a 4G54 manifold with the carb off a 4G63 depending on the EGR set up (I'm taking a guess at this as a possible option)