idle issues

[kindred4x]

Ok so i modded my throttle body, like the write up i found on this site(trim throttle shaft and butterfly screws) After i put everything back together the truck idled high, so luckily i had another TB so i put things back to stock. Still high idle in park about 1400rpm. When i accelerate then take my foot off the gas the trucks rpms slow down to about 1200 rpms, the truck will actually keep on moving without my foot on the pedal, i even tried this going up hill and the rpms never went down and the truck kept on rolling. I noticed that when im coming to a stop the rpms go down then when it should hit idle, the rpms flare up a little bit then go back down when im coming to a complete stop. At a complete stop in drive the idle seems fine when i shift from drive to park they flare up to around 1500rpms, and go down to maybe 1100-1200. My IAC is new, bought it after this mess, the throttle body is assembled correctly. vaccum line going into throttle body is hooked up and fine. TPS sensor is reading .91volts. Disconnected the battery couple times for 3o min each time also. I am clueless as to whats happening, and the flare in rpms when coming to a complete stop is really throwing me off. Can you guys help me out?
1996 4.0 OHV

 

[dogfriend]

I'm thinking that you have an air or vacuum leak somewhere that is causing the high idle. Maybe the throttle plate isn't closing fully or there is a leak somewhere nearby.

The IAC valve controls the idle speed by regulating bypass air past the throttle plate. If you have extra air from some other source, it can't regulate the idle slowly enough.