Replaced IAC Now have surging acceleration
 

I Replaced IAC because it was making this weird noise, the noise went away but now I have surging acceleration. I removed the battery let it set an hour, then let it idle for about 20 minutes. The surging is about 90% better but it will still surge from time to time. Usually during town driving. It did pop up a P106 code this morning. Any ideas? Forgot 2001 MPV

I have a possibly related issue. After taking my car to the shop to repair the intake gasket manifold, the car idled poorly (I have a '99 Mazda 626 with 135k miles). I replaced the IAC, and now the engine surges to about 4000 rpm for a few seconds after startup, followed by idle hunting between 1500-2000 rpm. The car drives fine with the IAC unplugged, but idles rough at 500 rpm, as expected with IAC unplugged.

Were you able to make any progress?

Throttle body?
 

I had the same surging problem in my 2003 Mazda MPV. There were several things going on at the time:
I had a vacuum leak, which was a torn rubber boot, so I replaced that. But the symptom persisted.
then I cleaned out the Throttle body AND the IAC with throttle body cleaner, and the symptom finally went away. No more surging acceleration.
My Mazda also still throws a code P 0031 (oxygen sensor), but that engine light has been on since I bought it a year ago. So I’ve been wondering whether that code has anything to do with creating the surging problem over the long term. (Running too rich causing buildup?) Not sure. But for now, surging is gone.
So you could try looking for vacuum leaks and clean out throttle body too.