What Am I Missing 1996 Ford Ranger Idle Issue.

I have a 96′ Ford Ranger 2.3L. I was originally pulling codes involving EGR (insufficient flow) and Ignition system (ignition coil 1 & 2). I like to think I’m a decent mechanic but I’m about to pull my hair out with this. I replaced the EGR, DPFE, PCV valve, and for safe measure I also replaced the IAC. I replaced it because I have had known several Ranger owners who had to have theirs replaced due to idle problems. I thought since it was was already off I would get it before it went out. I got everything back together. As soon as I started driving the truck is idling high. The check engine light stayed off for about 20 miles and is now reading P1506 Idle Air Cntrl Overspeed Error. I have checked all the vacuum lines, that are accessible without removing the intake again, with carb cleaner. I exchanged the iac thinking by chance I got a bad unit from the parts store. Nothing has improved this issue. On start up it idles roughly 1500rpm. When I drive it and stop at a red light, stop sign, etc. the idle stays around 2000rpms. If the heat is on when I stop it will idle between 2500 and 2800rpms. I just got a new TPS to put on it but what are my options beyond this, assuming it does not correct it? I’ve seen many owners online talk about what sounds like the same issue. I can’t find a vacuum leak. I’ve replaced almost everything dealing with the intake as far as sensors go etc. Any insight at this point would be great. If anyone needs more information I will give everything I can. Thanks. -Mike