New, weird problems
 

So my RPMs have been alittle weird for a long time now, but I finally learned to live with it. They used to, as I was comign to a stop, hold at about 1000 RPMs, but then the split second before the stop, they would drop down to about 500, and then raise themselves back up to normal idle while in drive. Now, I suddenly have even weirder RPMs, and another odd issue. First, the RPMs. I havent done anything under the hood in a few months, but now all of a sudden, my idle is at 1000 RPMs while stopped in drive, and while in park with the engine on, my RPMs are almost at about 1600. Also, when I shift into drive, it "bumps" into it, like the car is being launched forward for a split second. I will back out of my driveway, shift from Reverse to drive, and be launched forward. I have felt this effect before, when I had my transmission resister unplugged, but I checked on that, and its all fine, the resister was just replaced only about 4 months ago anyway. Also, as I was cruising down the highway last night, I had been driving for about an hour at this time, and was speeding, so I decided to left off of the gas and coast down to the speed limit. My Torque convertor was definetly locked up, because I took my foot off of the gas, ad my RPMs didnt dip one bit, and my speed remained pretty constant, but as I was coasting, it felt almost like the brakes were being tapped very lightly. Like I said, RPMs and speed remained the same, but I felt kind of a braking effect, very lightly, and very inconsistent. It was like I was tapping the brakes every 2 or 3 seconds. Thats the best way to describe it.
And the final issue that has arisen is that When im cruising at about 50 or so in town, where there is alot of stop and go, when I see a stoplight in the distance turn red, and I know I have to stop, I will let off the gas all the way, and coast most of the way in until I have to hit the brakes, but when I let off the gas, my RPM's will drop from about 2000 down to 1000, and then up to 1500, down to 1000, and continue liek that, wavering back and forth between 1000 and 1500, until either the gas or brake is applied.
All of these problems appeared within a day of each other, so they must be related somehow. Any help would be appreciated. Im thinking I might just need a new ECU, TCU, TPS, or possibly all 3.

i know the older legacys have an adjustment to the IAC motor... do the svxs?

I also think it's IAC related. Perhaps a good cleaning of the throttlebody is in order.

I just cleaned the entire throttle body and intake ductwork only about 3 months ago. So its not that. The IAC could be it though, except I am not familiar with its location, or how to clean or replace it.

Haven't done it myself but I know it's on the bottom of the throttlebody.