P0505 IACV, replaced it, but still having the same problem.
 

Okay guys I recently had the IACV valve act up on me again. I cleaned it out, but still no goose. I picked up a used throttle body from a 2002 TL-P and removed the IACV, cleaned it, and replaced it, but the problem is still there!
Another thing is that I recently bought a universal o2 sensor to replace the primary o2 that went out on me. I occasionally get a P0135 code for the o2 sensor, so what I'm wondering is whether this o2 sensor could have anything to do with the P0505 code I'm getting? If i reset the ECU, the rough idling problem goes away for a little while, and sometimes just turning the engine off and on will get it going normally for a while again. It revs up and down from 1000 to 1500-1700 rpm, then drops to 1000 again.

Thanks in advance for your advice guys!

i vacuum leak could be present and the code wrong ... do any work on ur upper intake mani ?

Problem was never found, but i got rid of the code. Went to the yard today to pick up a used type-s throttle body. however, when i got home, i purchased 4 bottles of carb cleaner, and sprayed down the whole intake manifold. then i installed the throttle body, and the car feels totally different. not sure if the throttle body fixed it, but a combination of everything solved the problem. just thought i'd update you guys on it. waiting for my o2 sensor to come in to solve the last problem :)