All the throttle stop screw does is stop the throttle plate from slamming into the TB bore and eventually cutting a groove in the TB throat. The basic adjustment is so the throttle plate just clears the TB throat.
The thing about the throttle stop screw adjustment is, minor adjustments may hardly be noticeable, the ECU corrects some for the idle change. Minor changes in the stop screw are like chasing your tail, you may get a momentary idle change, but the ECU eventually corrects and it ends up just about the same as before you fiddled with it. The ECU adjusts the pulse band width, fuel ratio and IAC. And any adjustment at the stop screw requires another TPS adjustment.
1300 RPM sounds like a vacuum leak, most likely in a sub system, heating, A/C controls, maybe the purge vacuum line or maybe the vacuum lines for the vacuum canister. I usually make up a handful of short pieces of vacuum line, around two inches long, with a screw in one end and plug off every vacuum inlet on the intake manifold, except the fuel regulator. Process of elimination, if the idle falls, plug them back up one at a time and see which one is causing the high idle, troubleshoot the sub system from there.
Like mentioned the TPS grounds can also cause issues. TPS controls timing and fuel to some degree along with inputs from other sensors. Replacing the TPS sensor may not help if the issue is in the wiring, connectors or the ground points themselves. I even had one idle problem that was from oil in the TPS connector. Some mechanic thought it was a good idea to spray the connector with WD-40 which turned out to be a bad idea. Many of my TPS issues caused what I call hunting at idle, the idle goes up, then down and then back up again, in 2-3 minute cycles. The exception is a really bad (water soaked) TPS then you may get a 2500 RPM idle. Or serious ground issues which may cause a Renix hot start, when the idle flairs way up right after a start. Sticky IAC or even charging system issues can also cause a hot start.
I always start out by plugging off all the unnecessary vacuum inlets on the intake manifold, re-torque the bolts for the intake/exhaust manifold, check the TB for tightness (the gasket shrinks with age) and ohm my TPS grounds. Eight times out of ten it is one of these 3-4 things causing the high idle issues.
You may also want to take a look at your charging system. Many times when my IAC started acting up it was because of a charging or battery issue. Not often a high idle issue, more often a stalling issue, sometimes a hot start issue. The IAC gets sluggish when the charging system is sick, Renix or OBD.
