I have a 1956 Dodge Regent with a 1992 318 Magnum that my grandfather swapped into it. Its had a high idle (around 1000 rpm) since it started running again. Recently, I replace the TPS, IAC, and MAP sensor, which fixed a few running issues and now it makes most of the power that it used to. I was hoping that the parts would fix the high idle, but it now idles around 1500-2000 rpm. It's at the point were I have to brace myself just to shift into gear. If anyone knows what the problem might be, it would be nice to hear about. Thank you.

Are you positive it's a magnum? 92 was the first year for them, Should be either a 53006714 or 53006657 casting # on the side of the block. Have you checked for vac leaks?

It is a magnum. I haven't found any vacuum leaks after spraying brake clean around the engine. It just started to idle high after I replaced the parts.

Reset the PCM.... Disconnect the battery, turn on headlights, turn off headlights, reconnect battery, turn key to "On", not start, don't touch anything, count to ten, start the engine. It should figger out idle pretty quick.

I did what you said, and it idled down to about 1200 rpm. It revs up and pops a little bit every few seconds, and it pops if I let my foot off the pedal while driving.

Throttle body clean? Seems like you have a vacuum leak somewhere there. Have you check the plenum? The intake is a two-piece design, and the gasket between them is notorious for blowing out.

I cleaned the throttle body when I replaced the parts. I wasn't aware of the plenum, but I will check and replace it when I have time.